Information

How does someone with red-green colorblindness see yellow on a monitor/television?


I recently watched the video This Is Not Yellow explaining how red, green, and blue pixels can be used to create images of all other colors. Since yellow is created with red and green pixels, how is a person with red-green colorblindness (me, for instance) able to perceive yellow on a monitor?


Normal people see color due to the bellow mentioned combination of red, green and blue:

But due to genetic factors, The graph Distorts:

Now,If consider the normal Color code for yellow:

Yellow = R(255) + G(255) + B(0)

Or in other words

Max. Red + Max. Green + no Blue = Yellow

That means even if you can see a little of Red and Green, you can still a little deeper or lighter shade of yellow.

So Summing it up in the images:

Normal

Red ColorBlind

Green ColorBlind

Blue ColorBlind

Source:

Coblis - Color Blindness Simulator

A quick introduction to colorblindness


Below is a summary of the information found here and from how Enchroma glasses work (although, I've tried the glasses and the effect is too subtle for me to wear them regularly).

Human color vision works because there are three different color-sensitive receptors called cones that detect short-wavelength light (bluish), medium-wavelength light (greenish), and long-wavelength light (reddish). The charts below show the sensitivity of these receptors in people with different genetics.

Chart taken from Color Art and Science, edited by Trevor Lamb and Janine Bourriau

The bottom chart, marked (c), shows the sensitivities of eyes of people with normal color vision. Short-wavelength (blueish) cones detect a distinct patch of light while the medium- (greenish) and long- (reddish) wavelength cones overlap, but are still separated enough to reliably distinguish between the two color ranges.

The middle chart, marked (b), shows mild protananomaly or deutananomaly color blindness in which the color regions that medium (greenish) and long (reddish) cones react to are more overlapped than in people with normal vision. This can lead to trouble distinguishing these colors since the overlap causes both receptors to light up for more colors.

The top chart, marked (a), shows complete protanopia or deutanopia, where the long (reddish) and medium (greenish) receptors completely overlap in their sensitivity ranges. This can also happen if one receptor is entirely missing from the retina.

I was under the impression that all red-green color blindness was of the protanopia/deutanopia type, meaning that the yellow generated on a computer screen should look red because the green light wouldn't be activating any of the non-functional medium (greenish) cones. In actuality, I only have a mild protananomaly/deutananomaly, so my eyes are still sensitive to the differences between red and green light, just less so than normal people. The yellow I see may be subtly different than other people, but I can still differentiate.

Enchroma glasses work for mild colorblindness by filtering out light in the overlap region of medium (greenish) and long (reddish) cones. This creates more separation in the detection region of those cones, thus making some colors more distinct at the cost of blocking some light.


How to Use Color Blind Friendly Palettes to Make Your Charts Accessible

According to Color Blind Awareness, color blindness affects 1 in 12 men (8%) and 1 in 200 women (0.5%). There are an estimated 300 million color blind people worldwide, including Mark Zuckerberg, Bill Clinton and Prince William!

Optimizing your graphics can help make them more accessible—and that doesn’t mean banishing color from your charts and graphs either. Contrary to popular belief, more than 99% of color blind people can, in fact, see color—just not in the same way as someone who isn’t impacted by color blindness.

In this guide, we’ll break down the different types of color blindness and their special considerations with respect to data visualization. We’ll also show you how to effectively use color blind friendly palettes to make your graphics available to a wider range of people.

We’ve put together some ready-made color blind friendly palettes to inspire you. Scroll down to the section 4 for that.


Living With Color Blindness

Here are some ways to work around poor color vision:

  • Memorize the order of colored objects, such as traffic lights.
  • Have someone with good color vision label and sort your clothing or other items that you want to match.
  • Use a smartphone or tablet app designed for people with poor color vision (which allows users to detect colors of objects).

If your child has color blindness, let teachers know that your child has trouble seeing certain colors.

Children with color blindness may have a hard time seeing yellow chalk on a green chalkboard, or reading assignments printed on colored paper or with colored ink.

Teach your child the colors of common items. This can provide a frame of reference for when other people are discussing colors in your child's presence.


Improving The Color Accessibility For Color-Blind Users

According to Colour Blind Awareness 4.5% of the population are color-blind. If your audience is mostly male this increases to 8%. Designing for color-blind people can be easily forgotten because most designers aren&rsquot color-blind. In this article I provide 13 tips to improve the experience for color-blind people – something which can often benefit people with normal vision too.

What Is Color Blindness?

There are many types of color blindness but it comes down to not seeing color clearly, getting colors mixed up, or not being able to differentiate between certain colors.

These problems can also be exacerbated by the environments in which people use websites. This could include low-quality monitors, bad lighting, screen glare, tiny mobile screens and sitting far away from a huge television screen.

Relying solely on color for readability and affordance makes a website difficult to use, which ultimately affects readership and sales.

Meet Smashing Online Workshops on front-end & UX, with practical takeaways, live sessions, video recordings and a friendly Q&A. On design systems, CSS/JS and UX. With Brad Frost, Stephanie Eckles, Carie Fisher and so many others.

While the following tips aren&rsquot exhaustive, they do cover the majority of problems color-blind people experience when using websites.

1. Text Readability

To ensure text is readable it should pass accessibility guidelines based on the combination of text color, background color and text size as follows:

Here are a few examples of color and size combinations that do and do not pass:

This illustrates how contrast is based on the combination of color and size. (View large version)

2. Text Overlaid On Background Images

Text overlaid on imagery is tricky because some or all of the image may not have sufficient contrast in relation to the text.

Text overlaid on an image without a mask. (Image credit: Jay Wennington) (View large version)

Reducing the background opacity increases the contrast, making the text easier to read.

Text overlaid on an image with a mask. (View large version)

Alternatively, you can style the text itself to have a solid color or a drop shadow, or anything else that matches your brand guidelines.

3. Color Filters, Pickers And Swatches

The screenshot below shows the color filter on Amazon as seen by someone with and without protanopia (red–green color blindness). Without descriptive text it is impossible to differentiate between many of the options available.

Color filter without labels as seen by someone with protanopia is impossible to use. (View large version)

Amazon shows descriptive text when the user hovers, but hover isn&rsquot available on mobile.

Gap solves this problem by adding a text label beside each color as shown below:

Color filter with labels as seen by someone with protanopia is easy to use. (View large version)

This happens to be beneficial for people with normal vision too. For example, black and navy are difficult colors to differentiate on screen. A text label takes the guesswork out of it.

4. Photographs Without Useful Descriptions

The screenshot below shows a SuperDry T-shirt for sale on its website. It is described as “Leaf Jaspe” which is ambiguous as leaves can come in an assortment of colors (green, yellow, brown. etc.).

It's hard for color-blind people to know what color this SuperDry T-shirt is. (View large version)

Jaspe (or rather “jaspé”) means randomly mottled or variegated, so using this in addition to the specific color would be useful: “Gray Green Leaf Jaspe.”

5. Link Recognition

Links should be easy to spot without relying on color. The screenshot below simulates the vision of somebody with achromatopsia (can&rsquot see color) viewing the UK Government Digital Service (GDS) website. Many of the links are hard to see. For example, did you notice that “GDS team, User research” (located under the heading) are links?

GDS blog as seen by someone with achromatopsia. (View large version)

To find a link, users are left having to hover with their mouse waiting for the cursor to change to a pointer. On mobile, they are left to tap on text hoping it will make a page request.

The links above with icons are easier to see. For those without, it would be a good idea to add an underline, which is exactly what GDS does within the body of its articles:

Underlined links are easy to see by someone with achromatopsia. (View large version)

6. Color Combinations

In the physical world you can&rsquot always control which colors appear next to one another: a red apple may have dropped and nestled itself into some green grass. However, we can control the colors we use to design our website. The following color combinations should be avoided where possible:

  • green/red
  • green/brown
  • blue/purple
  • green/blue
  • light green/yellow
  • blue/grey
  • green/grey
  • green/black

7. Form Placeholders

Using a placeholder without a label is problematic because placeholder text usually lacks sufficient contrast. Apple has this problem with their registration form, as shown below:

Apple's registration form uses a placeholder without a label. (View large version)

Increasing the contrast is not advisable because it will then be hard to tell the difference between placeholder text and user input.

It&rsquos better to use labels – a good practice anyway – with sufficient contrast, which is exactly what Made.com does as shown below:

Made.com uses labels with good contrast. (View large version)

8. Primary Buttons

Often, primary buttons use color alone to present themselves as such, and Argos does just this on its login screen:

The Argos login screen relies on color to emphasize the primary button. (View large version)

Instead, consider using size, placement, boldness, contrast, borders, icons and anything else that will help – within the bounds of your brand guidelines. As an example, Kidly uses size, color and iconography:

Kidly uses size, color and iconography to emphasize the primary button. (View large version)

9. Alert Messaging

Success and error messages are often colored green and red respectively. Most color-blind people don&rsquot suffer from achromatism, and so will naturally associate different colors with different messages. However, using prefix text such as &ldquoSuccess&rdquo or, my preference, an icon makes it quick and easy to read as shown below:

Alert messaging with text prefixes and icons. (View large version)

10. Required Form Fields

Denoting required fields with color is a problem because some people may not be able to see the differences.

Denoting required fields by color. (View large version)

Instead, you could consider:

  • Marking required fields with an asterisk.
  • Even better, marking required fields with “required.”
  • Where possible, remove optional fields altogether.

11. Graphs

Color is often used to signify different segments of a graph. The image below demonstrates how people with different vision would see this. The color-blind-friendly graph is on the right.

Graphs viewed with normal vision (View large version) Graphs viewed with protanopia (View large version) Graphs viewed with achromatopsia (View large version)

Using patterns and, where possible, placing text within each segment makes graphs easy to understand. When text doesn&rsquot fit – as is often the case with a small pie chart segment – using a key will suffice.

12. Zoom

One accessibility feature that browsers have, is enabling someone to zoom in as much as they need. This improves readability&ndashwhich is especially helpful on a mobile device.

Unfortunately, zoom can be disabled using the Viewport Meta Tag, which is problematic. For example, text size may be too small to read in relation to the color contrast—but zooming in effectively increases the font size, making it easier to read. So don&rsquot disable zoom on your website.

13. Relative Font Size

Similarly to the previous point, browsers provide the ability to increase text size (instead of zooming the entire page as a whole), in order to improve readability. However, some browsers disable this functionality when the font-size is specified in absolute units such as pixels. Using a relative font size unit, such as ems, ensures that all browsers afford this capability.

Tooling

There are lots of tools available to help you design for color-blind people:

    : if you have an existing website, you can just enter a URL and receive feedback of what needs to be improved. : provide two colors to see if they pass accessibility guidelines. : apply color blindness filters to your web page right within Chrome. : a color blindness simulator for Windows, Mac and Linux, showing you what people with common color vision impairments will see.

Conclusion

The tips in this article are not exhaustive, and they are not necessarily applicable to every situation. However, they do cover the majority of problems color-blind people experience when using websites.

It&rsquos more important to take away the principles, so that you can integrate them into your own design process. Ultimately, websites aren&rsquot just meant to look good – they are meant to be easy to use for everyone, including people who are color-blind.


2 Answers 2

Visolve is the software that transforms colors of the computer display into the discriminable colors for various people including people with color vision deficiency, commonly called color blindness. In addition to distinguishing colors and finding a specific color, it aims to help people with color blindness:

- to guess a normal color, and
- to feel the color gradations in natural scenery etc. by their visual information.

Visolve can execute the following three types of color transformation, filtering, and hatching:

Red-Green transform -- transforms redder colors to brighter, and greener colors to darker,
Blue-Yellow transform -- transforms bluer colors to brighter, and yellower colors to darker,
Saturation increase -- increases the saturation of all colors,
Filtering -- darkens all colors other than the specified color, and
Hatching -- draws different hatch patterns depending on color.

When people with color blindness apply, for example, Red-Green transform, if they keep the above transformation rule in mind and see color changes, they could guess a normal color. Moreover, Red-Green transform reflects the degree of color saturation into its brightness regularly. So they could know not only the difference between red and green but also the difference between two reds, i.e., the degrees of red.

It lets you play with images to see the effects.
It's available for Windows and Mac OS X, and is free for personal and non-commercial use.

By using Visolve Toolbar, you can apply color filter to the entire screen with just button click without the capture operation. The toolbar will appear by selecting "Visolve" in "Toolbars" in the taskbar context menu.

Moreover, the toolbar appears at the Internet Explorer by selecting "Visolve" in "Toolbars" in the view menu. You can apply color filter to the whole Explorer's window area without the capture operation.


How does someone with red-green colorblindness see yellow on a monitor/television? - Biology

Basically, they cut out some parts of the spectrum where the cones in a colour blind eye overlap a lot.

"There are two types of red-green color blindness: deutans and protans. Deutans, which are 75% of cases, have a defect in the green cone cells. In this case, the defect causes the green cone cell to be spectrally shifted towards red. Green becomes more like yellow. Protans, which are 25% of cases, have a defect in the red cone cells. In this case, the defect causes the red cone cell to be spectrally shifted towards green. Red becomes darker and more like orange.

These spectral shifts degrade the quality of color information sent to the brain. Some colors like blue and yellow are not affected, but shades of green, orange, brown, red, pink and purple are muddled and washed out. If the color blindness is strong, it can be difficult to correctly name these colors, causing problems with jobs and many everyday tasks. People with red-green color blindness can usually see between 10,000 to 100,000 shades of color.

The EnChroma Cx uses a special extra-strength version of the Digital Color Boost™ coating. By removing the wavelengths of light where overlap is occurring between the red and green cone cells, the spectral shift can be reversed, amplifying the color signal sent to the brain. The result is that colors appear to be brighter and more pure. Thousands more shades can be seen. Colors can be recognized more quickly and with less confusion. For many, the effect is a profound emotional experience."

Here is a good graph showing how sensitive each receptor is to different wavelengths of light:

But we don't perceive colour directly from these receptors. Instead, our visual systems combine the output of these receptors to form three channels: black vs. white (L+M+S), red vs. green (L-M) and blue vs. yellow (S-(M+L)). This is why there is no such colour as a reddish-green or a bluish-yellow our visual systems are not able to perceive these (except under exceptional laboratory conditions). As you can see in the graph, the L, M and S receptors aren't just receptive to pure red, green and blue but to a range of wavelengths centred near these colours, and they all overlap to some degree. But the L (green) and M (red) receptors overlap quite a bit.

In red-green colour blindness, either the L or M are shifted so they're even closer. This means that the red vs. green (L-M) channel is no longer able to distinguish between the two, so this channel is always close to zero and the person no longer sees either red or green just something muddy in between. Blue-yellow colour blindness is similar, but in this case it's the S channel that's shifted towards the L and M. In this case it overlaps with both and this means there's no longer any colours that activate the S without also activating L and M (and vice versa), making it impossible to distinguish blue from yellow.

These glasses work by notching out the parts of the spectrum where the receptors overlap the most. Assuming this works as described, they claim that this increases the relative difference between their outputs, making it easier for colour blind folks to distinguish the colours.


Am I at risk for color blindness?

Men have a much higher risk than women for color blindness. You’re also more likely to have color blindness if you:

  • Have a family history of color blindness
  • Have certain eye diseases, like glaucoma or age-related macular degeneration (AMD)
  • Have certain health problems, like diabetes, Alzheimer’s disease, or multiple sclerosis (MS)
  • Take certain medicines
  • Are white

If you think you may have color blindness, talk with your doctor about getting checked.


Changizi Blog

There are those among us who are “health blind”, i.e., handicapped at sensing the health signals most of us easily recognize on others around us. They are the color blind. But we at O2Amp can fix that.

1. The Health-Blind Among Us

Despite the presence of modern electronic medical sensing tools, medical personnel still rely on their naked-eye visual skills when examining and judging the symptoms and health of patients (Savin et al. 1997).

But it is not widely appreciated that approximately 5% of medical personnel – 10% of men and 1% of women – are “health blind”, i.e., they are severely perceptually handicapped at sensing the health symptoms of patients. And they – and those that hire them – often don’t even realize.

Who are these “health blind” medical personnel?

Although not widely appreciated, it has long been documented that red-green color-deficients are disabled at seeing veins, vasculature, pallor, cyanosis, jaundice, rashes, bruising, erythema, retinal damage, ear and throat inflammation, and blood in excretions (Dalton 1798 Wilson 1855 Best & Jaenel 1880 Little 1881 Ahlenstiel 1951 Logan 1977 Voke 1980 Steward & Cole 1989 Spalding 1993, 1995, 1997, 1999, 2004 Currier 1994 Anthony & Spalding 1999, 2004 Campbell et al. 1999, 2004, 2005 Reiss 2001 Cockburn 2004 Cole 2004 Changizi et al., 2006, suppl Table 1 Spalding et al. 2012). Even 18th century scientist John Dalton, who was color blind, observed that he “could scarcely distinguish mud from blood” (Dalton 1798).

Even today 10% of the 500 most prevalent medical conditions list skin color changes amongst the symptoms (Changizi & Rio 2009), and a red-green color deficient’s deficit in discriminating reds and greens makes him or her unable to see these everyday health color signals on the skin.

Color deficiency can consequently lead to medical misdiagnosis (Campbell, 1999 Campbell et al., 2004, 2005), and has at various times prevented entry into medical school (Hiroshi, 1998).

If you’re red-green colorblind, then you’re health-blind. And among those not traditionally deemed color deficient, many are mildly so, and thus mildly health-blind.

The graph below shows the reported clinical difficulties among 42 color-deficient doctors surveyed by Spalding (1995). (It should be kept in mind that this particular graph shows reported difficulties, and thus does not capture what the color-deficient doctors don’t realize they’re missing.)

Self-reported clinical perception difficulties from 42 color-deficient doctors (Spalding, 1995).

2. Color-Deficiency is an Especially Severe Problem for the Medical Profession

A variety of occupations (e.g., pilots, police) routinely require passing a color exam before entry, and in some countries passing a color exam is even required in order to get a driver’s license.

But, except in rare instances (e.g., Hiroshi, 1998), color blindness had not been a formal barrier for becoming a doctor.

Unfortunately, a recent discovery by researchers at our 2ai Labs ( http://2ai.org ) shows that color blindness is not just a problem for medical personnel, but a disproportionate problem for the medical community.

In 2006, we showed that color vision evolved specifically to distinguish health and emotion states on the skin: our peculiar primate variety of color vision evolved to be optimized for sensing the oxygenation modulations hemoglobin undergoes under the skin (Changizi et al., 2006).

Red-green color vision is uniquely about seeing oxygenation, and therefore red-green color-deficients are especially hindered at seeing the skin signals that underlie health signals. Unlike other fields where colorblindness is a handicap but where it is actually fairly unlikely to find perfectly indiscriminable colors to a color-deficient, the oxygenation variations of blood under the skin are completely invisible to the red-green colorblind because they’re missing the evolved machinery specifically designed to detect it.

Color blindness is consequently a critical issue in clinical settings for patient health. Approximately 5% of clinical personnel are handicapped at detecting everyday health signals on the skin (including seeing veins, for example), and yet many are not even cognizant of their handicap. (And neither are the many other personnel who are only mildly color-deficient (sometimes due to aging).)

Color deficiency is also a serious liability issue for medical staff and their employers, and color deficient doctors have been sued on this basis (see citation to News & Observer).

3. The O2Amp Medical Solution for Color-Deficiency

Historically there has been no solution for the color deficient clinician. Varieties of filtered eyewear for color deficients exist that can help them pass Ishihara tests or perceive certain discriminations among objects in the world. But none were designed to enhance the signal that primate color vision evolved to detect: oxygenation variations in the skin (Changizi et al., 2006). And thus no previous color blindness treatment was consistent with the health perception demands of medical personnel.

We at 2ai Labs, having discovered the evolutionary function of color vision, were in the unique position to design optical technology to enhance the signal for which color-deficients are deficient. In particular, we created O2Amp, our company highlighting several distinct optical technologies for enhancing perception of facets of the blood under the skin.

For color deficients our flagship technology is our Oxy-Iso Colorblind Correction Medical Eyewear, designed to amplify and isolate the oxygenation signal coming from under the skin. Color-normals use the eyewear to enhance perception of veins, but color-deficient medical personnel use the eyewear to amplify their minimal baseline sensitivity to oxygenation variations in the skin.

The Oxy-Iso doesn’t merely aid color deficiency…

…the Oxy-Iso aids color-deficiency in a manner consistent with the symptom-, vasculature-, and health-perceptual needs of doctors, nurses and other medical personnel.

[See O2Amp’s site – http://o2amp.com – for testimonials and more information. Also see the following for example results on the Farnsworth-Munsell Test: https://changizi.wordpress.com/2013/01/29/the-ravenous-color-blind-new-developments-on-o2amp-for-color-deficients/ ]

“I wanted to let you know how much I have enjoyed using your eyewear, especially the Oxy-Iso glasses. I now use them in all of my leg vein procedures. Being color blind makes finding deeper (reticular) cutaneous veins a challenge the Oxy-Iso eyewear makes them much easier to see… We actually have the Christie Vein Viewer (one of the IR devices) in our office… Although it is a very cool product, it does markedly alter the appearance of veins and the treatment process itself. While I haven’t used the IR device much for sclerotherapy, I use my Oxy-Iso’s every single time.” – Daniel Friedmann, MD, Cosmetic Dermatologic Surgery

“This is exciting. I have not been able to see colors my entire life… They really work. I recommend them.” – Cary M. Silverman, MD, ophthalmic surgeon, Eyecare 20:20. Video review.

“I had to try them, working in the Dental field, colors are very important in many aspects of my practice. They vary from instruments identification, diagnosis of the oral cavity, and many other aspects. I went from the muted colors that I was used to all my life, to what I perceive as a more bold, and brighter red and greens. To me the darker red shades, like maroons and burgandy colors are more lighter with the oxy-iso on. I went from not seeing any numbers on the online color blindness tests, to seeing most of them. It has been stated that there may be some limitations of these online test due to screen settings and ambient light. But going from seeing nothing to almost all of them is truly remarkable to me.” – DKH, DDS, Glen Cove

“After 20+ years of medical education, I had a healthy skepticism about these glasses. I mean, how can you “cure” color-blindness, my cone cells have a mutation and my brain has learned to adapt. My eyes simply can’t absorb light at those frequencies. But, I was intrigued. As a surgeon, being color blind has not affected me as much as you might think, texture is very important, as is consistency, and I think I rely on those cues all the time. However, I do have a problem telling if something is bile-stained versus just bloody, and dark bloody emesis I could only tell by the smell. But as an art lover, and flower lover, being color blind is just annoying. Not to mention trying to shop at places like J. Crew where all the stupid colors are like, “stone” and “sledge”. What? // Anyway, I bought these on a lark, and OH MY GOD, THEY WORK. I only get 1 right on the Ishihara color blindness plate test (red-green and some blue-yellow deficiencies), but with these glasses, I got more than half right! It makes everything brighter and so much more intense! I scrolled through a website of Impressionist paintings and it was incredible! Beautiful!! I can see red flowers on trees now!! I can see the red on birds’ wings!! it’s actually almost overwhelming, I don’t wear them very often because it makes me a little sad that I’ve lived 44 years with a muted palette. I haven’t tried them in the OR yet, but I’m on call Wednesday. . . Makes me wish I’d invented or invested.” – Dr. Marie Crandall, Associate Professor of Surgery, Northwestern University Feinberg School of Medicine

“Currently, I occasionally try them during orthopedic surgeries, but mostly during speys and castrations. Some of the pregnant or recently pregnant dogs/cats (especially cats) have large networks of enlarged superficial vasculature just beneath the skin, and the glasses can be beneficial in identifying and avoiding these during the initial incision.” Dr. Aaron Raney, color-deficient veterinarian


The answer is controversial. Hume, 18th century British philosopher, famously argued that such a possibility is conceivable, that if we are presented with a spectrum of color where some intermediate shade is missing we will be able to imagine the missing shade, even if we never saw it before. Here is Hume's missing shade of blue thought experiment:

"Suppose, therefore, a person to have enjoyed his sight for thirty years, and to have become perfectly acquainted with colours of all kinds, except one particular shade of blue, for instance, which it never has been his fortune to meet with. Let all the different shades of that colour, except that single one, be placed before him, descending gradually from the deepest to the lightest it is plain, that he will perceive a blank, where that shade is wanting, and will be sensible, that there is a greater distance in that place between the contiguous colours than in any other. Now I ask, whether it be possible for him, from his own imagination, to supply this deficiency, and raise up to himself the idea of that particular shade, though it had never been conveyed to him by his senses? I believe there are few but will be of opinion that he can."

Curiously, this observation goes counter to Hume's own empiricist doctrine that all our ideas come from sense impressions, and are not created by imagination, other than by combining them. But "it is hardly worth altering a general thesis for one exception, which is very much the line Hume himself adopts", according to Jenkins. In the 20-th century Jackson suggested another famous thought experiment about the matter, Mary the color scientist, but came to the opposite conclusion, although admittedly the Jackson's setup is far more unfavorable to Mary than Hume's.:

"Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specializes in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like 'red', 'blue', and so on. She discovers, for example, just which wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal cords and expulsion of air from the lungs that results in the uttering of the sentence 'The sky is blue'. [. ] What will happen when Mary is released from her black and white room or is given a color television monitor? Will she learn anything or not?"

Jackson's answer is that she will learn, Mary could not have "imagined" colors on her own no matter how much she knows about them. The difficulty with deciding who is right is that it is unclear how exactly we can determine, in actual experiment, what exactly was "imagined", and compare it to what was intended. This is at the heart of the current philosophical debate about the so-called qualia, private "feels" or experiences. It is also unclear if we can trust subject's opinion on whether the "imagined" missing shade was the same as the "right" shade presented to her afterwards. Wittgenstein had serious doubts that the talk of private sensations is even meaningful, let alone trustworthy, see How does Wittgenstein's argument against recognizing private sensations work? and What is the role of sensations in Wittgenstein's private language argument?

See a discussion of both thought experiments in Johnson's How I Got the Blue. For a modern scientific look at color perceptions see Bimler's Psychological Color Space and Color Terms.

Yes, you can imagine new "colors", and there are physically meaningful complex colors that humans don't really see.

Short version

We see with our eyes, and those signals go back to our brains. We ascribe "color" to things that we see as colors are common patterns worth noting and exploiting, e.g. for communication.

Since this question is about imagining a new color, sure, you can imagine a description that doesn't correspond to anything else that you've seen. In the absence of correspondence to physical reality, this would seem to be a pointless exercise, but there's no reason why you can't imagine it.

Additionally, there're physically meaningful "colors" that we actually observe in science labs. However, you can't really "see" these colors directly as the human brain's visual processing center isn't wired to process them.

Colors with more dimensions

Another answer had mentioned the prospect of tetrachromacy which is sorta how animals with more sensory inputs can see things they'd have a wider color space. However, this strikes me as a limited perspective because that seems to suggest that there's something special about seeing color in just 4 dimensions.

You can perform a Fourier transform on a source of light waves to get infinitely many dimensions of color as opposed to just the 3 in human vision or the 4 in tetrachromacy. We've even built machines that do exactly this, i.e. Fourier transform spectrometers.

It's somewhat difficult for a human mind to appreciate such complex "colors" in the same sense that we perceive normal colors though. For example, here's a very high dimensional color for a blue flame. Assuming that this plot uses 1 data point per /nm on the x-axis from 300/nm to 700/nm, then that's a 401-dimensional color.

Even if you were to see the blue flame yourself, it'd look blue to your eyes, as your eyes don't have the spectrometer's mechanisms for seeing more. However, you can see the color through the spectrometer's eyes by observing the spectrum showed in the link. If you want to imagine it in your own eyes, it'll look like a blue flame, since that's what it is but if you want to rewrite how your mind works, you might try to appreciate that it's a far more complex color than just "blue".

Science note: The reason that we have such spectrometers is because more detailed colors can tell more about what you're looking at. In many labs, spectroscopy is the go-to method for identifying chemical compounds and other physical samples.

Not much art

When people talk about imagining new colors, I suspect that they're generally looking for something aesthetically pleasing. The problem here is that beauty is in the eye of the beholder you can imagine a Fourier-transform-like visual apparatus, which would see in vastly more colors than humans normally do, but since imagining such complex colors would require a lot of work and rewiring one's own brain, it's doubtful that an observer would find aesthetic joy in it.

Aesthetics seem to work best when an observer can relate to what they see on some level. Unheard of colors, such as high-dimensional colors from spectrometers, probably won't match up to this for most folks.

Color blindness

Some people can't perceive colors like normal, i.e. they're color-blind. At least in some cases, this results from the eyes lacking the physical hardware to pick up on some of the color signals.

Looking through Google, it appears that some folks are claiming that they're getting close to a cure for some sorts of color blindness, presumably by fixing the eyes. Once a life-long color-blind person has their eyes fixed, will their brains be able to fully process and appreciate the color distinctions as though their eyes had picked up on the signals all along, or will their brains have pruned the unused informational channels?

It seems trivial to imagine something that is almost like blue, but different. Some can even imagine a super-intelligent shade of the colour blue. It does, however, bring up the challenge of defining what a "color" is. Pick the wrong definition, and you find it mathematically impossible for there to be any colors besides the ones we can see.

A curious case, however, arises with red-green or blue-yellow. Can you imagine a red-ish green or a blue-ish yellow? They're hard colors to comprehend. In fact, they're called Impossible Colors in the cognitive science world. It is currently believed that our concept of color is built from "opponent processes." Red and green are opponents, so you can only observe one or the other. Same for blue and yellow. This is why alternating lines of them clash so heavily.

If you can imagine a reddish green or a bluish yellow, you can imagine an impossible color, which in theory you have never seen.

There is some evidence to suggest that it is possible to observe one of these "impossible colors" by having one eye view one color and one eye view the other. It's debatable whether this color actually existed, because it depends entirely on the fusion between the two eyes, and yet some people do insist it exists.

Under normal circumstances, there is no hue that one could describe as a mixture of opponent hues that is, as a hue looking "redgreen" or "yellowblue".

In 1983, Hewitt D. Crane and Thomas P. Piantanida performed tests using an eye-tracker device that had a field of a vertical red stripe adjacent to a vertical green stripe, or several narrow alternating red and green stripes (or in some cases, yellow and blue instead). The device could track involuntary movements of one eye (there was a patch over the other eye) and adjust mirrors so the image would follow the eye and the boundaries of the stripes were always on the same places on the eye's retina the field outside the stripes was blanked with occluders. Under such conditions, the edges between the stripes seemed to disappear (perhaps due to edge-detecting neurons becoming fatigued) and the colors flowed into each other in the brain's visual cortex, overriding the opponency mechanisms and producing not the color expected from mixing paints or from mixing lights on a screen, but new colors entirely, which are not in the CIE 1931 color space, either in its real part or in its imaginary parts. For red-and-green, some saw an even field of the new color some saw a regular pattern of just-visible green dots and red dots some saw islands of one color on a background of the other color. Some of the volunteers for the experiment reported that afterwards, they could still imagine the new colors for a period of time.2

Some observers indicated that although they were aware that what they were viewing was a color (that is, the field was not achromatic), they were unable to name or describe the color. One of these observers was an artist with a large color vocabulary. Other observers of the novel hues described the first stimulus as a reddish-green.

Curious what such a color might feel like? Some people claim that if they cross their eyes such that the crosses in the picture below overlap, they see yellow-blue, an impossible color. Of course, to go much further would start to explore the question of whether color is a "real" thing or an "illusion." Perhaps all colors are, indeed, imaginary. I make such a statement, of course, to tie the answer back to philosophy, but you have to admit that the cognative science side of the answer is rather fascinating!


Web resources

Create your own color schemes&mdashand check how they look to a color-blind person&mdashwith this great interactive color chooser.

Another good one, but without the color-blindness test.

Sample color schemes—analogous, split complementary, triadic—with HTML color codes, at Color Wheel Pro.

Color schemes with great examples from the work of Monet, Van Gogh, Toulouse-Lautrec, etc.

Good explanation of various aspects of color & how it's used (scroll down to the second half of this article).


Watch the video: Δείτε την οθόνη του κινητού στην τηλεόρασή σας (January 2022).