Color Blindness Myths and Misunderstandings

October 25, 2010

Topics: Accessibility.

I’ve always believed that web site accessibility depends on an understanding of accessibility issues — not on technical issues. Obviously, knowing the technical side of web site construction and how it impacts accessibility is very important. Some decisions are fundamentally technical, but a huge part of web site accessibility is purely visible — and just understanding accessibility issues will make a huge difference.

To that end, here are a few quick comments about color blindness. Color blindness (or color perception deficiency) is an issue for approximately 1 in 12 people, mostly men. However, color perception problems are not always very effectively diagnosed, so these numbers could be low.

Color blindness is an inability to see certain colors.

Color blindness is really a misnomer. People with various types of color blindness are better described as being color vision deficient: it’s an inability to distinguish colors, not an inability to see color. People at the furthest limits of color deficiency, however, may have such an extreme inability to discern colors that this can be a fairly accurate description.

Individuals with color vision deficiencies can’t see red.

Well, no. Assuming we’re discussing Protanopic or Deuteranopic color blindness, in which the individual is missing either the red or green sensitive cones, the actual problem is that they may not be able to distinguish the color red. The color isn’t readily differentiated from other hues of the same shade or tint. Red perception deficiency is certainly the most common type of color vision deficiency, but it’s certainly not true of all individuals with poor color vision.

You have normal color vision

Not really. In fact, color perception is a spectrum for all of us. What’s commonly referred to as color blindness is actually only the portion of that spectrum which is considered anomalous — where the ability to perceive color begins to impinge on normal interactions with the world. Having “normal” color vision simply means that you don’t generally experience problems because of your color vision. You may well still fail an Ishihara test.

Color perception deficiencies are inconvenient, but don’t pose any serious problems

Particularly in our modern, technological society, color perception is a critical part of comprehending the world around you. From LED indicators which blink red, green, or yellow; to weather maps which a spectrum from red to green indicating storm severity; to knowing what color a traffic signal is showing if you’re in a location with a different signal orientation than what you’re familiar with. Outside of technology, color deficiencies can impact recognizing that you’re developing a severe sunburn or knowing whether you’ve actually cooked that hamburger enough to be safe.

People with Color Perception Deficiency have better Night Vision

Actually, I couldn’t definitely verify this one way or the other. There are a number of claims that this is true, but the reasoning is highly variable and not particularly evidence-based. It’s possible that certain types of color perception deficiency may give people better night vision, but it’s also possible that since some types of color perception deficiencies cause people to be photosensitive, those people may feel like their night vision is better, simply because it’s much better than what they’re accustomed to. Regardless, any evidence which is reasonably definitive would be appreciated.

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30 Comments to “Color Blindness Myths and Misunderstandings”

  1. Strange&SillySavage; March 4, 2011 at 4:36 am

    O Yea of Little Faith! I was drafted because of my peculiar phase shifted “color-blindness” ability to see very subtle shades, naturally enforced from birth “mental training” to differentiate objects by outline and texture, and superior night vision which is more than double a “normal” persons contrast in low level light. All of my abilities were well verified by extensive vision and field testing by our military. So I got to be point man on every night patrol, the guy with the crossbow who took out sentries, forward spotter/observer ashore to call in fire from ships and aircraft, and a helicopter gunner (which I really hated!). Yes, In our last forever war in Southeast Asia, I saw and killed the “camo” clad enemy before they saw me! So for me, my “color-blindness” is a curse and a blessing. A curse because it sent me to war, and a blessing because it helped me survive it!

  2. I’m moderately to severely colorblind, not sure if it’s anamolous or the -nopic severity. But I usually fail all those tests, miserably. Colors I get mixed up with range from blue and purple, to orange and green, to brown and red or brown and black and commonly brown and green. It’s those browns and purples that mess me up thd most. Luckily I’ve only had one experience in school where my deficiency affected me. But usually I can’t distinguish blue from purple. And I’ve accidentally colored things like the sky purple in like art class when I was in elementary school. But I’m not exactly sure if I have enhanced night vision or not. I haven’t really tested it out or noticed. As for camouflage, again I haven’t tested to see if I could see the object with camo or not. But I’m sure I could. Well I’m glad to read these articles though, because I get to relate to others with the same disability and plus it’s really interesting, so that’s awesome.

  3. Re:- Colour perception-v-night vision.

    I have slight deutan deficiency, not notieable for practical purposes but would fail the Ishihara test, though not the Farnsworth S15, for what it is worth.

    However, my night vision is definitely better than average. When navigating at night or viewing the night sky, it takes much less time to become accustomed to darkness, only a minute or so; not the usual twenty minutes or more. Also, the customary use of averted vision in these circumstances makes no noticeable difference. When walking at night in a group and on many other occasions, it was apparent that I was able to see clearly obstacles that others could not see at all. Except in a totally enclosed space, such as a room with no windows, it is never so dark that I can see nothing.

    Experts always seem reluctant to acknowledge this colour to night vision relationship, on the grounds of lack of evidence; indeed, any mention of the subject is usually met with silence. Could this be a reluctance to accept that a condition normally regarded as a deficiency actually embodies a sizeable benefit? Where would this leave the condition of ‘normal’ colour vision?

    It seems likely that this is an evolutionary legacy from early mammals, which were nocturnal and had a greater requirement for night vision than colour vision.

    Perhaps it is time for objective night vision tests to be devised, and conducted as matter of course, in conjunction with colour vision tests.



  4. I am only mildly color deficient. i have relay trouble with light green light pink (see them as grey of can not tell then apart) dark green dark red (see them as black). i have good night vision but i rock at hunting. I always spot game faster than color normal friends and family. camo is less effective on my one of my students found every person in that camo commercial instantly (he also failed the color plate test). this hunting advantage could be why this is genetic issue is so common is humans.

  5. I see 70 on the plate where I should see a 29 for the link about the ishihara test. I’ve since done some searches and it’s the same with this color blindness test and this one where I can’t see anything on plate 13. I have never been diagnosed for this before, but I wonder how accurate these things are. I’m certainly going to bring it up to my GP. It seems like this is a test you can get from amazon too, though it’s expensive. Thanks for this article.

  6. Another colour blind web dev here, red/green/brown is hard for me as is anything in the blue/purple/violet range.

    I was interested to see some people mention that c/b people have better night time eyesight. I’ve can vouch for that as I’ve had plenty of times where I could distinguish certain features at night when normal sighted friends couldn’t. Don’t really know why, it just is that way. I guess it might be because my eyes aren’t distracted by all those darn colours!

    Back to the web, the one thing that developers can do is *always* underline text links (with the excpetion of “obvious” link blocks such as main navigation). That way you can get away with using more similar text/link colours and not worry about it too much. Unfortunately removing them is all too common, along with not styling :focus links but that’s another story.

  7. Not experimental evidence, but it’s commonly thought that early mammals lost most of their color vision because they were nocturnal. It was regained only very recently: we humans only share this capability with apes and old world monkeys.

  8. Well, this is certainly very interesting! I’m glad that this article has spawned this discussion. Although I’m still not certain that this constitutes proof positive that people with color vision deficiencies have improved night vision, there’s no question that it’s a very common thread of personal experience — which points in the direction of truth, at any rate!

    Thanks for all your responses!

  9. I am color blind (fail 3 on the test) and my wife is not. We have frequent power outages at night and I am the first to find the lighter / candles. She’d have no clue they were where I picked them up from. I wear glasses too (shortsighted) but she has perfect vision. This is the first time I am reading about others who experience this.

  10. I will definitely agree with color vision problems and camouflage, although my understanding is that the military has figured out how to make camouflage that works against those with color problems also. I have some red-green weakness and I think I was like 12 or 13 before I understood what camouflage was supposed to be–most every example of it I saw stood out like a sore thumb to me.

    Just because it blends in well for someone with normal color vision doesn’t mean it blends in with abnormal color vision.

  11. I’m colour blind, in the sense that i can’t tell the difference between brown, red and green. i can sometimes make correct intelligent (or so i think!) guesses. However I really do see better at night than my girlfriend for example. It’s little consolation for not fully enjoying the full spectrum of colour nature provides, but at least if i get stuck down a mine it might help!

  12. Hey Joe!

    I must say that I’ve never heard about colour blindness and having better night vision. Interesting.

    It would also be interesting to see if there’s a correlation between the severity of colour blindness to more effective night vision. Get snopes on the case πŸ™‚

    I personally fail in only one circle on the Ishihara test (the 6). I do know that my eyes adjust quite quickly to the dark. As well, I’ve never had a problem driving at night time.

  13. @Matthew My husband is color blind and he was able to spot deer in the fields last weekend as we drove home at twilight. They were almost invisible to me as they blended into their background but he saw them easily as distinct shapes. He speculated that it was a result of his color blindness. I think so. There are advantages, this could correlate with sharp shooting. He mentioned that color blind men were put at the front of the lines because they were able to spot camouflage. Here’s a short article about the upside of color blindness:

  14. @joe: wonderful. that is a fantastic tool. thanks for sharing!

  15. @marlene Thanks for the tip! I’ve fixed the link.

  16. hi joe, just letting you know the link to the vision simulator is broken πŸ™

  17. @Matthew I’ve read that as well; but again, without any definitive evidence.

    @Karl What I wonder about that is whether that perception is because you’re more accustomed to identifying what you can see with reduced color or because you can actually see better. Given that one of the characteristics of low-light conditions is a significant reduction of color definition, I’m wondering whether the real issue is in the ability to understand what you’re seeing, rather than actually having improved perception in low-light conditions. From a subjective perspective, this may give you better understanding of your surroundings in low-light, but not actually mean that you have better vision. Does that make sense?

  18. re: Night Vision. I have no evidence, but I am very color blind (as in usually can’t get any of the items in the Ishihara tests) and I seem to have much better night vision than most people.

  19. Thanks for clearing things out. Very good and interesting read.

  20. I’ve heard a similar rumor that colorblind individuals are better sharpshooters, with the justification being that your retina packs in more rods, which give you a higher resolution image. I’d like to see the Snopes on that one (although I still like to repeat it πŸ™‚ )