Category Archives: Thoughts

What is it Like to be Color Blind

Laura Evans created a nice and short documentary film to show what it’s like to be colorblind. While interviewing a colorblind artist she gives us a nice overview of how it feels, some thoughts on what the term color means and how important colors really are if you are suffering from color blindness. “No such thing as color” includes some nice details to give you an insight on how it might feel to be colorblind.

There is only one thing which I don’t really understand: She starts with letting the guy name the coloring of some houses in the neighbourhood. For me as a strongly red-blind person the guy in the film does a perfect job on this task…. but watch yourself :-)

You also might like to visit Laura’s website at

5 Questions about Color Blindness

Lily is working on a school project about color vision deficiency. She’s on the way to write a paper about it and has some questions which I would like to answer in this article.

Question 1: What are your feelings on the recent discovery regarding monkeys and a possible cure for their colorblindness? Do you think that it is legitimate, and do you think it should be used on humans in the future?

I think we have to look at this in a broader view. Personally I don’t believe that one of the big problems of our society is to cure color blindness. But scientific work in this area—genetic eye treatments—may help us to understand much better how we can help other people and heal some severe diseases.

And if there is a breakthrough why shouldn’t we use it on humans? Every person should be free to decide if he or she wants such a treatment or not.

Question 2: Do people affected by monochromatism look at life differently? Do they have less emotions because they live in a black and white world?

Yes, definitely. If you are suffering from monochromatism you are not only living in a gray world but also are severely sensitive to light, long sighted and more. This for sure makes your life look different.

Besides that if we only look at the world in gray colors I also think, that this changes a lot. You will see other things as all the colors don’t disturb your perception. Of course you will also not see certain things as the brightness difference might be to small for your eyes. There are certain things which you would struggle with but overall I would say if you are suffering from monochromacy you don’t look at life differently, but just at the world if you have to fulfill and live in a surrounding created by people with color vision.

And I don’t see any relation between emotions and colors because even little babies show a lot of emotions before they really can see colors at all.

Question 3: Should public schools be required to incorporate information about colorblindness in their science curriculum?

No I don’t think so. There are so many interesting scientific things which we can learn at school and color blindness doesn’t need a special treatment in this curriculum.

What I think should be done is to teach the teachers on the topic of color vision deficiency. Every teacher should at least once hear about it and maybe know some techniques to help colorblind students. I strongly believe that every colorblind pupil will find its way through school perfectly and teachers could support this if they sometimes only would know a little more about it.

Question 4: Are there any alternative attempts to cure colorblindness that you are aware of? If so, how affective are they?

There are people who claim, that corrective colored lenses or glasses can cure your color blindness or also some Chinese medicine techniques claim to help. Personally I don’t believe that there are some other possibilities to cure a color vision deficiency.

In 99% of all cases color blindness is encoded in your chromosomes. Therefore you can’t just adjust something easily or push some hidden trigger to cure it.

Question 5: What social disruptions can colorblindness bring upon a person’s life? Teenagers lives in particular. I am colorblind and my mom and sister are both artists. I can not take art class, interior design, yearbook, or any classes like that because of my condition. Can you think of anymore?

Just recently I received an email from a 15 year old boy who is getting teased by his classmates because of his color blindness. So this really can be a problem but I suppose this doesn’t happen to often and is only a problem at a certain age.

Of course, there are certain jobs you can’t accomplish as a colorblind person. Jobs which relate on color vision as their primary task like the ones you mention, or jobs which need good color vision usually for safety reasons. This often causes a lot of frustration among people who realize that they can’t start a career of their dreams, which I fully understand.

But many other people also can’t make their dreams come true. We have two possibilities to follow in this case. Either we work towards better regulations, better aids and tools, and better education in the topic of color vision deficiency. Or we have to accept that not every dream will become true in our lifes.

Do Color Blind People Perceive a Colorful Life?

Sarah contacted me to learn more on how color-blind people perceive our colorful world. Everybody can generate images which simulate this visual handicap with my color blindness simulator Coblis. But this isn’t the whole story, as those pictures can’t tell you how colorblind people think about this colorful—or in this case colorless—world.

Sarah put together some really interesting questions concerning the perception of color and how I handle this as a quite strongly colorblind man. Here are my answers to her questionnaire:

Colorful Dancer

Colorful Dancer

Sarah: I’m interested in the perception of color to one’s self, mostly. How do you describe colors to yourself (when others are not around)? For instance, what does ‘colorful’ mean to you? Do you conjure up an image of rich blues, yellows, and whites, or do you include red and green (what you perceive to be red and green, anyway) in that definition?

Colblindor: I included this picture as an example for what colorful means to me. If it includes red or green, I can’t tell you. So I can not tell you which colors I explicitly include to name something colorful as I can’t name them. I would say a colorful thing needs at least three to four clearly distinguishable colors for me. This could also be a fire truck red and a grass green combined with some blue or yellow. On the other side I can tell you that there are certain pictures which are not colorful for my eyes but seem to be colorful if you are not colorblind yourself.

Sarah: In your own mind (just yourself, all alone), do you describe the world around you in shades of blue and yellow, or do you throw red and green into the mix? For example, if you saw a brightly lit Christmas tree, would you say to yourself that you see a lot of blue and yellow lights, or would you describe colors you think might be red, green, purple, etc.?

Colblindor: If you dig a little deeper into the topic of color blindness you can learn, that moderate to strong color-blind people have problems along the whole color spectrum (see Colorblind Colors of Confusion). I am strongly red-blind and therefore have also problems for example with blue/violet/purple or blue-green/gray/purple. — Personally I would say I don’t attach color names to my visual perception. I only name them when somebody else asks about it and this very often puts me into a position, where I just can’t name it or even describe it properly.

Sarah: Do you describe things to yourself as being red/green/etc. when the situation does not call for a need to tell the exact color? For example, grass is green and everyone is taught this at a young age, but when you’re just walking around by yourself, do you ever mistake grass for being yellow/another color (before remembering it’s green)?

Colblindor: As I described above I don’t really actively perceive colors attributing names to them, only if I learned the color of something (green grass). In this case I just know the color name but don’t clearly perceive it. Therefore I can’t really say that I sometimes mistake anything for having a wrong color. Sometimes I get confused if I know something always has a certain color (for example red) and I perceive it completely differently. In this case I ask myself if this is really the color it should be or if the source of the problem is somewhere else.

Colorful Rainbow

Colorful Rainbow

Sarah: I can use certain color filters that show me what some images might look like to someone with a color vision deficiency. To my color normal eyes, these filters for red-green deficiency make a rainbow look like a streak of yellow in the sky. Is that how you would describe it too? If not, how do you perceive it?

Colblindor: Rainbows look like rainbows. Rainbows are not to colorful for my eyes but anyway a beautiful phenomenon. In colors I would say blue-something-yellow-some other color streak. By the way, the picture wall on this image looks very colorful to me, even if I can’t tell you at all which colors I see.

Sarah wants to learn a lot more about color blindness. She says: “I’d love to talk to anyone with any form of color vision deficiency”. So if you feel like chatting just contact her directly at

Rainbow photo by Cavin

Everybody is Color Blind

Are you colorblind? No, you don’t think so? — I am sure you also have some form of color vision deficiency or colorblind sensations. You don’t believe me? I’ll prove it in the following article.

I would like to show you four types of color blindness which are true for almost all of us. Starting with a very simple form we will definitely get into more details when it comes to small-field tritanopia, which strongly supports my statement that everybody is colorblind.

(A) Colorblind in the Darkness

When it is getting dark at dusk colors start to fade. You start to mix up colors and are not so sure any more when it comes to naming a specific color. So one could say that everybody is colorblind in the darkness.

I know this is not such a strong argument to support my statement, but it is a very good example to get an impression of how it feels like if you would have some form of color vision deficiency.

(B) Ultraviolet and Infrared Blind

Non of us can see both far ends of our color spectrum: infrared and ultraviolet. We name those colors but we can’t see them. This doesn’t necessarily means we are colorblind if nobody can see them anyway. But there are creatures who can see those colors.

A lot of people heard that bees can see ultraviolet light; which is true. But they don’t have a broader color spectrum as they also have only three different color receptors like people with normal color vision. Bees see less reds and more blues, that’s not really better than us isn’t it.

But there are some fish, some turtles and the whole family of birds who can perceive our whole color spectrum and also ultraviolet light. Birds have four different color receptors (tetrachromats) and clearly can see more colors than you and me. On the other side we have for example rattlesnakes which have some form of infrared eyes which can see the prey at night.

(C) Tetrachromacy

If you believe it or not but not only animals are tetrachomats but also humans can have four different color receptors!

Studies have shown that women who carry the color vision defective gene, can develop four different receptors in the eye and therefore have a broader color spectrum than the rest of us. This is a very rarely diagnosed phenomenon but definitely makes all of us colorblind compared to tetrachomatic women.

(D) Small-Field Tritanopia

And if you think the three points above don’t really prove that we are all colorblind this last point will definitely change your mind.

Normal color vision means you have three different color receptors: one peeking at red (L-cones), one at green (M-cones) and one at blue (S-cones). Together we have about 4.5 million of those receptors distributed all over our retina. Most of them are L- and M-cones and only about 7% are blue sensitive.

A closer look at the distribution of the color receptors shows, that in the very center of the retina, inside the fovea, there are no blue cones at all! As this spot is very small—you can think of visual field the size of a tennis ball at the other side of the court—this is called small-field tritanopia. See also my article about tritanopia to learn more about this type of color vision deficiency.

So in the center of our visual field we have no S-cones. This means only L- and M-cones can give us information about the colors in that spot and therefore we are all dichromats in the fovea. — And why do you don’t know anything about your central color blindness? Because your eyes don’t really focus on such a little point but often move around. This makes you believe, that you have trichromatic color vision over your whole visual field.

And because small-field tritanopia is true for all of us, everybody is at least a little bit colorblind! quod erat demonstrandum.

Color Blind: Which Are Your Blind Colors?

Here is an interesting definition of blind colors: “Colors that are not or not completely recognized by a gray-level scanner.” When I look at my personal color blindness this fits quite well. Compared to people with normal vision I sometimes really think that my eyes are some type of advanced gray-level scanners—but not more.

What I am looking for are the colors we colorblind people have problems to see or distinguish.

color confusion protan deutan tritan
red/orange/yellow/green X X
brown/green X X
Threshold green to white X X
Threshold red to white X X
blue-green/grey/red-purple X
green/grey/blue-purple X
red/black X
green/black X
violet/yellow-green X
red/red-purple X
dark blue/black X
yellow/white X

This first list of colors which are confused by color deficient people is taken from the book Diagnosis of Defective Colour Vision by Jennifer Birch. It is important to know, that these colors are only mixed if there exists no luminance contrast.

From my perspective as a strongly red-blind (protanopia) guy I would say the above list is a quite good image of my color perception. They do also fit with the colors along the so called confusion lines of the corresponding type of color blindness.

I would like to add my personal list of color blind colors which I often can not distinguish. And I also would like to add some examples to them, so somebody with normal vision might be able to imagine a little bit how it feels to be colorblind.

Protan Confusion Colors

dark red/black: If I get an email with words highlighted in red, I can’t see them.
grass green/orange: I couldn’t spot an orange laying in my lawn.
leaf green/red: No red blossoms in trees and no red apples in trees.
bright green/yellow: I can’t see if a banana is ripe or not.
indian summer colors: It’s colorful, but I have no chance to name the colors.
dark blue/violet: I’ll never know what the difference is.
cyan/gray: All shades of blue-green look truly colorless to me.
brown/green/red: Please, don’t talk about red animals in the forest.

I suppose there are many more shades and colors I can’t really see. But this is a list of colors which I often come across and have big problems to identify and classify.

So what are your colors of confusion, problem colors, color blind colors? It would be very interesting to hear also from you which colors cause you the biggest problems.

Named Pencils for the Colorblind

If you are suffering a moderate to strong color blindness, it’s always a hassle if you have a crayon box in front of you full of colored pencils. – How about naming them? Could this help?

Named Non Colored Crayons

A french student from a packaging design class had just this idea. All white crayons named with the corresponding color.

Her professor says: “After all isn’t color subjective? Think of the colorblind people for example. So here’s the objective set of color pencils.”

Ok. I am colorblind and think about it. And I think it’s of no use for us colorblind. Why?

As a colorblind person I have great difficulties in seeing, differentiating and specially naming colors. So if I see a certain color I can’t tell you if it is red or green, because I can not see it.

Now, let’s imagine I grab a colored pencil which is just plain white only with its color name printed on it. I actually don’t really know how this color looks like as I don’t know which name corresponds to the color I see. Ok, if I know the color of a certain thing it could help (I learned that leaves are green—most of the time). But otherwise the name is not a clue for me at all.

What I need is to see the color so I can compare it if it really is the one I need. And even if I see it, there is still a big chance that I still will mess them up. So names are for nothing and colors are unfortunately not much better.

Red-Green Color Blindness Doesn’t Exist

Hey, everybody knows that red-green color blindness is the most common type of color vision deficiency. How can I claim that it doesn’t exist at all? – I’ve got not only one but three reasons which support my statement that there is no type of color vision deficiency which really deserves the name red-green color blindness.

Red and Green Peppers

Only Gray Peppers?

When you realize or get told that one of your friends is colorblind, most probably you remember the term red-green color blind and try to imagine, what this means:

  • My friend can neither see red nor green?
  • He can’t distinguish those two colors at all?
  • Besides red and green he has no problems with colors?
  • Or maybe red and green look like gray to him?

This is all wrong and the reason why I say, that there is no such form of color deficiency which should be called red-green color blindness. And here are my three arguments which strongly support the sentence: Red-green color blindness doesn’t exist.

(1) Red-green color blindness doesn’t exist, because there are really two distinct forms: red-blindness (protanopia/protanomaly) and green-blindness (deuteranopia/deuteranomaly). Protan defects are caused by a shift of the peak of the red sensitive cones in your eye towards the green peak, or if they are missing at all. For deutan defects the same is true for the green sensitive cones. And even if the naming sounds like a combination of both, you are suffering just under one of them.

(2) Red-green color blindness doesn’t exist, because if you are colorblind you will encounter problems with colors from the whole color spectrum. There is no such color vision deficiency which is only focusing on certain colors like red or green. The so called confusion lines can give you a quite good understanding of how a color spectrum is seen by color blind people.

(3) Red-green color blindness doesn’t exist, because if you are really colorblind, you really can see only in gray. This is called monochromacy or achromatopsia, which affects only a handful of all color blind people. In this case it doesn’t make sense to talk about any colors at all. On the other side, if you have only problems with your red, green or blue sensitive cones, this isn’t actually color blindness but some form of color vision deficiency. Or as I put it in another article: Color Blindness is not ‘Color Blindness’.

If you still think, that you are suffering from red-green color blindness, have a look at Which Type of Red-Green Color Blindness is It? and learn more about the real type of your color vision deficiency.

Foto taken by Martin LaBar

Red-Green Color Blindness doesn’t mean You can’t Distinguish Red from Green

Often people think that if you are suffering from red-green color blindness you can not distinguish red from green at all. But they are wrong.

The term red-green color blindness isn’t accurate and doesn’t describe the actual color vision deficiency correctly. If you have a look at the confusion lines of the CIE 1931 color space you will see, that there are many different lines in the color space which connect undistinguishable colors to a colorblind person. Therefore a red-green color vision deficiency makes you colorblind to many more colors than just red and green.

Red Green

red green red green taken by Crystl

On the other side it depends strongly on the brightness and saturation of colors to make them hard to distinguish if you are colorblind. Colorblind people often develop some sort of color intuition which is based not only on the hue but also on the brightness of the color they see. Something which is hard to imagine if you have normal color vision.

For example some shades of red are close to green, others close to brown and again others are even close to black. The following list shows a few examples of colors which look close to each other and can’t be distinguished easily if you are suffering from red-green color blindness:

  • yellow — bright-green
  • orange — grass-green
  • apple-red — leave-green
  • dark-green — brown
  • blue-green — gray — purple
  • dark blue — violet

As a conclusion you can say that some reds and some greens are very well distinguishable. It depends very much on the brightness and the saturation of each color to make them undistinguishable for a red-green colorblind person.

Sunsets, Rainbows, Stop Signs for Colorblind Guys

John Trask is 76 years old and is Dealing with color-blindness is whole life. He says,

“I’ve never seen a sunset or a rainbow.”

Is it really possible that somebody can’t see a sunset or a rainbow because of his color blindness? – I can’t believe it.

SunsetWith not seeing a sunset he can only mean not to see the beautiful colorized sky and sun during a sunset. Seeing the sun going down behind the horizon can’t be a problem even for a colorblind person. And to my eyes also some beautiful colors can be perceived.

I’m red-blind, or at least strongly red-weak. And a sunset can be something really beautiful even to me. Of course, it will never be as colorful as for a person with normal color vision. But isn’t everything just less colorful for us colorblind guys?

RainbowAnd it’s the same for a rainbow. I can definitely see a rainbow—just less colorful.

A rainbow consists of the whole color spectrum and this with a blue sky or gray/white clouds in the background. So if you can’t see a rainbow, you must not be able to distinguish all colors either against blue or gray. And this could only be the case, if you suffer from a complete color blindness.

I don’t believe, that somebody with red-green color blindness can’t see a sunset or a rainbow. You can see them, but just less colorful as everything else on the world.

Stop SignBut what I agree on is another of John’s statements.

“Stop signs disappear,” Trask said. “The white lettering I can pick out, but [the rest of the sign] just fades into whatever is in the background.”

What are your experiences with sunsets, rainbows and stop signs?

Pictures by vtveen, Mundoo and overundulate.

How to Color Charts Respecting Color Blindness

If you are suffering some type of color vision deficiency you definitely know those situations: You try to read a beautifully colored chart, whereas the biggest challenge turns out to be matching the legend to the appropriate part inside the chart itself.

All the different type of charts usually have one thing in common, they have a color coded legend. This looks very nice and helps to differentiate between the labels and the information you want to highlight. But this doesn’t take into account, that colorblind people might have great difficulties to match the correct labels to their counterparts or even tell the different segments apart from each other.

Blue Yellow Graph

Blue Yellow Graph

Just recently the guys from evolgen asked A Question for the Colorblind, where they try to find good colors for some informative charts. The solutions vary between using only shades of gray and random color suggestions from non-colorblind people. I don’t think this is the right answer to the question on how to color a chart taking into account also colorblind readers.

Scott from Standardzilla tries to go a more elaborate way. He is looking for good color combinations and analyzes the color contrast as well as the simulations of different color vision deficiencies. Introducing his thoughs with Color Blindness and Graphs and analyzing it at Colour Contrast Chart for Colour Blindness.

I propose we even have to go one step further. Here is my recipe on how to color charts respecting color blindness in three steps:

  1. Start with the theory of color blindness. The confusion lines are a great resource to discover colors that are and aren’t distinguishable by all three types of color vision deficiency.
  2. After you have chosen some colors which are not on the confusion lines of neither protan nor deutan nor tritan defects, enhance the color contrast as much as possible, while adjusting the brightness of each color.
  3. Check the adjusted color combination with one of the many available color blindness simulation tools. If the simulated colors look to close to each other, start all over again.

This three simple steps are not as easy to follow as it sounds. I suppose it will consume quite some time to really find the best colors for your colored chart while having in mind, that also colorblind readers should be able to catch your information easily without spending to much time on color legend deciphering.

There are also some quicker ways to improve the readability of your charts:

  • Patterns: Not only use colors but also patterns to mark your charts.
  • Label Inside: If possible, label the charts inside themselves or…
  • Label Outside: …attach each label to its segment (e.g. around a pie chart).
  • 1 Color and Brightness: Use only one color and alter only its brightness.
  • Grayscale: And of course, you can use just different shades of gray.

If you either try to find some good colors for your chart which suite everybody—even the colorblind people among us—or if you take a quick-win doesn’t really matter. Just bear in mind, if you offer a chart with a bad color choice, one out of ten males might have problems with its readability, which doesn’t really help to get your point across.