Here's everything you think you know, but don't, about colourblindness

When you look at that blob above, what do you see?

I don’t see much of anything — just a bunch of reddish-brownish-greenish circles. (Ask me to tell you which ones are which and I’d have to think for a minute.) Other colourblind people, apparently, might spot the digits 21. Sighted people should see a 74.

Assuming you aren’t colourblind as well, you can see what I can’t because the cone cells in your eyes work better than mine. Cone cells detect colour, while rod cells detect light and dark.

I’ve known I was colour-blind since I was about three years old, on a walk to Bee Creek Park in College Station, Texas. My dad, holding my hand, pointed out trees with leaves turning red for the start of autumn. I had no blasted idea what he was talking about, and told him so. He wasn’t too surprised. After all, there had been a 50% chance I’d turn out (as my school friends would later call it) colour-stupid.

Colourblindness (or stupidity) is, in the great scheme of things, hardly a great problem in life. I’ll never get to fly a commercial airliner or fighter plane. Some video games maps and heads-up-displays are confusing to me. Once or twice in my lifetime I’ve driven through a red light on an empty road at night. And pretty much every data visualisation on the internet looks like a mess.

But the real frustrating part of colourblindness, for me at least, is how little most people seem to understand it. Here’s a typical scene in the life of a colourblind person:

Dopey friend: Wait, you’re colourblind?! You never told me!

Colourblind individual: It, uh, never came up.

DF: What colour is this? Points to stapler

CI: That’s a black stapler.

DF: OK. What colour is the sky?

CI: Blue.

DF: What colour is grass?

CI: Green.

DF: What colour is —


DF: What colour is this? Points to shirt.

CI: I don’t know.

DF: Oh my god, you can’t see my shirt! Do I look naked to you??

In the grand scheme of things, of course, this falls squarely into the not a big deal category of irritants. The oppression of colourblind people is decidedly not a thing. But still, lots of people don’t understand what colourblindness is. And most colourblind people I’ve spoken with agree that over a lifetime that confusion gets pretty annoying. So I’m going to clear up a few things.

What even is colourblindness? How do you catch it?

The most commons forms of colourblindness are genetic conditions, passed along the x-chromosome. People with an x-chromosome and a y-chromosome only need their one x to be defective to catch it. People with two x-chromosomes need both to be defective.

Most women have two x-chromosomes, and most men have an x-chromosome and a y-chromosome. That’s why colourblindness is much more common in men than in women.

My mother’s father was colourblind. He had one defective x-chromosome, which he passed to my mother. But my mother has two x-chromosomes. Her
other x, which she got from 
her mother, works fine. So she isn’t colourblind. But she is
 a carrier.

That means that when she has a child, she has a 50% chance of passing that defective x-chromosome along.

My father, Ed, passed me a y-chromosome. And my mother passed me her defective x, so I’m colourblind. If they had a child tomorrow with two x-chromosomes, that child would have a 50% chance of becoming a carrier like my mother. If my father were colourblind as well (he isn’t), that two-x-chromosome child would have a 50% chance of being born colourblind. 

If they were both colourblind, all of their children would be colourblind.

OK, ok. Enough genetics stuff. What is it like to be colourblind?

OK. First things first. If it weren’t for all of you colour-sighted folks around telling me I’m colourblind, I’d never know it.

Like many colourblind people, I’m what’s called “red-green colourblind” as a shorthand. True, black-and-white colourblindness where the world looks like an old-timey movie is actually pretty rare. And it’s probably a lot easier for you to imagine.

My world looks pretty colourful. Red, green, yellow, orange, purple, blue, pink. Name any of those colours and I can form a clear picture of it in my head, think of a thing in the world that I’ve seen as that colour.

But there are a whole lot of reddish, greenish, brownish things in the world that other people seem to see as distinct shades. Nearly everything other people describe as purple I see as blue. Sometimes white things turn out to be pink in other people’s eyes. 

The real mystery arises with all the in-between shades. Some of them I can spot well enough — royal blue, baby blue, and sky blue for example.

But there’s a whole universe of hues that are mysterious to me. I can almost never recognise crimson, auburn, or salmon unless they’re pointed out to me. The same holds for most purples. I’m told there are colours with names like indigo, teal, and yellow-green, but I’m not sure I believe it.

Can you show me what it’s like to be colourblind?

Probably not. Some tools on the internet claim to convert images to show what they would look like to colourblind people. I can’t step outside my own visual experience to evaluate them from a neutral perspective, but I’m doubtful.

Here’s why.

Wavelengths of light, which our brains interpret as colour, are objective features of the universe. And I can point toward certain wavelengths and say they’re indistinguishable to me. But I can’t describe for you or visually represent the reddish-greenish colour my brain churns up when my cones send a signal saying “well, it’s one of those.”

Here’s a photograph that has a lot of colour in it:

What does it look like to you? What does colourfulness look like? What is it like to see in full colour?

You can’t explain that to me, not really. And I can’t explain my muddier vision to you any better. I can turn down the saturation on reds, greens, and purples, like so:

But colourblindness is a confusion and conflation of colours, not just a desaturation. So neither of us can really know what each others’ perspectives really look like.

I’ve been trying Enchroma colourblindness “correction” lenses lately and mostly they seem to make green traffic lights look a lot greener and people look a lot more orange. But their job is to make it easier to distinguish colours, not induce true colour-slightness.

Similarly, I have no idea what it’s like to be blue-yellow colourblind (a rarer form). Confusing blue and yellow? Those people must be crazy!

How can I be less annoying and more helpful to my colourblind comrades?

Ah! Finally, a simple question.

  • Don’t ask us to tell you what colour our shirt is. We know what colour our shirt is! It’s [inaudible].
  • Avoid colour-coding things when possible. When colour-coding is necessary, stick to bold, primary colours and try to spread them over as wide an area as possible. It’s much harder for us to tell these two colours apart, using only thin crowded text,   t h a n    t h e s e  t w o   c o l o r s , using nice spread-out colour blocks.
  • Remember, confusing colours is not the same thing as not seeing that colour exists. If you put a colourful thing on a white background, we can probably tell it’s there. (Probably.) We just may not know what it is.
  • If we get a colour wrong, just correct us! But, like, also keep in mind that this has happened about a million times in our lives and we may not find it as hilarious as you do.

That’s all there is to it, really.

Wait, I think I might be colourblind!

Cool! Luckily, it’s super easy to test for. This page (made by the same people who make those glasses) can tell you if you’re colourblind, and what sort of colourblindness you have.

Actually, whether or not you’re colourblind, you’re super colourblind.

Even if all the cones in your eyes function perfectly, you can’t see anything close to “all” of the colours. You see significantly more than I do, just like I see significantly more than a person with a more severe visual defect. But your eyes still round infinite wavelengths of light in the visual spectrum into just a few million colours.

Some people, known as tetrachromats, have extra cones in their eyes and see millions more colours within the same wavelengths that you see. Concetta Antico, a tetrachromat, described her vision to New York Magazine like this:

I see colours in other colours. For example, I’m looking at some light right now that’s peeking through the door in my house. Other people might just see white light, but I see orange and yellow and pink and green and some magenta and a little bit of blue. So white is not white; white is all varieties of white. You know when you look at a pantone and you see all the whites separated out? It’s like that for me, but they are more intense. I see all those whites in white but I resolve all these colours in the white, so it’s almost like a mosaic. They are all next to each other but connected. As I look at it, I can differentiate different colours. I could never say that’s just a white door, instead I see blue, white, yellow-blue, grey …

… Let’s take mowed grass. Someone who doesn’t have this genetic variation might see bright green, maybe lights or darks in it. I see pinks, reds, oranges, gold in the blades and the tips, and grey-blues and violets and dark greens, browns and emeralds and viridians, limes and many more colours — hundreds of other colours in grass. It’s fascinating and mesmerising.  

Try to picture that. Really imagine what it’s like. See how impossible that is? That’s what it’s like when you describe your colour vision to us.

And there are animals with even more cones that can see even more colours in our wavelengths, as well as many creatures that can see deep into the ultra-violet and infra-red ranges. Radiolab dedicated a beautiful segment to this phenomenon.

I hope this was helpful for some of you poor colour-sighted folks out there. If not, oh well! At least you get to know what “chartreuse” looks like.

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