Colour Blindness

I am colour blind. As was my brother, both my mother’s brothers, and my great grandmother. It runs in the family. More specifically I am red-green colour blind, and even more specifically appear to be suffering from Protanopia, an absence or at least weakening of the red portion of the spectrum. Most colour blindness, particularly red-green colour blindness is due to a recessive genetic condition on the X chromosome. Men, with only the short Y chromosome, have no way of masking the recessive gene and so are much more likely to express the condition. Colour blindness in some form is quite common. Around 8% of the male population in Australia has some form of colourblindness with Red-Green being far and away the most common, although some may have it mildly enough not to realise it until made do a screening test. Colour blindness was first described scientifically in 1794 by the chemist John Dalton who diagnosed himself and published the paper Extraordinary facts relating to the vision of colours. For a long time afterwards colour blindness was known as Daltonism.

When I tell people I’m colour blind, you usually get the same set of questions. What colour is the grass, the sky etc. These questions are annoying but I guess understandable. My answer always is that the sky is blue and the grass is green and that these are basically definitional to most peoples conception of colour. The issue with colour blindness is distinguishing between colours, in my case any colour involving red. Thus green, brown and red can all look very much the same, particularly when there is either not strong light, or there is only a small amount of the colour.

A fire truck in the day looks red due to the volume and brightness, but to distinguish between a red and green line on a graph is very difficult. Actually my reception of red is bad enough that it looks much darker. As a child I remember thinking that blood, in a drop was black. Blue and purple and all the nearby variants are also a problem. Cyan looks very close to white. Jacaranda flowers are much the same colour as the sky, and I could quite readily believe that Larvatus Prodeo was a blue blog.

All this causes less problems than you may think. Actually for most of my life the main thing that it provided is amusement to my family and friends. Like my brother and I accidentally bringing green bananas home – certain green and yellows can also be a problem. Or the time at primary school I coloured in a bright green Uluru, or coloured in a soldier for Anzac day one half green and one half brown. I could see a difference, but I just thought I had pressed harder one side. Another problem was the use of red chalk on a blackboard – pretty much invisible to me. Once I got out of primary school things got easier.

The reliance on colour for young children is how my mother became aware of my (older) brother’s colour blindness. He brought home what was ostensibly a reading test, saying “Draw a green tree”. Peter drew a brown one and it was marked wrong as a reading error. My mother knowing Peter could read quite well and aware of the family history asked him to read it. He did it perfectly and then she asked him to pick out a green pencil. He picked out a brown one.

With the exception of people colour coding things (an accursed practice) its not something that is really a problem. Sure colours are everywhere, but the fact that you do actually have colour vision, just reduced, and that you’ve lived with it your entire life with the condition you’ve learnt to intuitively adapt.

Every so often though it throws up a surprise as I realise how I rely on things differently to people with full colour vision. A good example of this is when I discovered a friend of mine didn’t know what colour traffic light was at the top. I was horrified, but then I asked more people and yes at least 30% would get it wrong and another 30% or so would get it right without confidence ie. guessing! When I thought about it I guess its natural that if you don’t need to know the order you won’t learn it. Not that I have a real need to know the order, I can actually tell them apart easily but it appears I’ve made an extra effort unknowingly to give myself some extra assurance.

During my final write up of my PhD, I would get corrections from my supervisor marked in red pen, and I remarked to one of my fellow students, that I thought it was a stupid convention marking mistakes in red rather than blue because it was much harder to distinguish from the black print. He said to me “red stands out on the page”. Suddenly I understood after all this time. People used red for corrections because it stands out on the page to them. To me of course it blends in with the black and it is difficult to see such things as additional commas etc.

I’ve never encountered a situation where this is true, however apparently the colour blind can be better at distinguishing certain kinds of things such as camouflage because they are naturally tuned to looking for say, variations in intensity rather than variations in colour. Mostly I find that bright red Christmas bush just blends into the general brown of the foliage.

Some professions are off limits. Electricians for one, and for a long time a commercial pilots licences was also disallowed, although now due to a number of cases through the Australian HREOC, by a Dr Arthur Pape, you can get a commercial pilots license although most of the big companies still won’t take you. I read Australia was the first place in the world to allow colour blind commercial pilots, but many other’s have followed suit. Essentially they showed while the colour blind may fail a test, it didn’t mean they couldn’t in practice perform as well as a normal vision person. Many other areas including army combat units and commerical driving licenses were also restricted although mostly these have now been lifted. None of these are things I ever wished to do so it was always ok.

The science that has lead from colour blindness is interesting. As I mentioned earlier Dalton was the first to scientically describe it, the first record we have of this is in a letter he wrote some of which can be seen here thanks to google books. In it he says:

I am at present engaged in a very curious investigations: – I discovered last summer with certainty, that colours appear different to me to what they do to others: The flowers of most of the Cranesbills appear to me in the day, almost exactly sky blue, whilst others call them deep pink: but happening once to look at one in the night by candle light I found it a colour as different as possible from day light: it seemed very near to yellow, but with a tincture of red: whilst no body else said it differed from the daylight appearance, my brother excepted, who seems to see as I do.

Which very well sums up the sorts of things that the colour blind experience, including the familial association.

Colour blindness was important in showing that the human eye perceived three colour (red, green and blue). The idea that any colour could be composed of these primary colours was first proposed by Thomas Young, but was later developed further by James Clerk Maxwell, who showed that colour blindness would be the result of an individual who lacked one of the predicted three colour receptors, and so gained acceptance for the three colour theory of light.

We now know that colour blindness is a recessive genetic disorder. The rate of occurance of colour blindness would tend to indicate that it is not a big issue with natural selection however it has been observed, that populations of hunter-gathers have the lowest rates of colour blindness, followed by agricultural and then industrial societies. This suggests that while being able to distinguish ripe fruit, was a big issue for survival, it has become less of an issue as civilization has advanced. An exampe of relaxed selection. Indeed few species have trichromacy old world primates being the main candidates and it has been suggested that this developed specifically to be able to distinguish ripe fruit.

This review of the Handicap of abnormal colour vision is interesting. I read through the list of difficulties faced with a strong sense of acknowledgement, although I don’t find most of them big problems. I’m well used to working around them. I would always, for example, get someone else (now its my wife) to pick paint colours. I dress fairly simply to avoid anything too bad in colours I wear, and I have learnt other ways to select ripe fruit like smell (doesn’t always work) or just asking people. I’m fortunate working with numbers and computer code that I have little need to deal with colours, only the occasional graph.

I seem to have a moderately severe case. I’m worse than most other people I have met with colour blindness, but I know others can be worse. To me though it seems a pretty mild impediment, and in many ways I enjoy the different perspective it has given me on the problems of perception.

Update: I have another post with some links to other pages on colour blindness and the experience of being colour blind.

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14 Responses to Colour Blindness

  1. Sacha says:

    Ah Steve, does the public holiday tomorrow give you the luxury of blogging past midnight?

    Just more on-topic, I’ve noticed that whenever I look at something through one of my eyes, it appears slightly more red and slightly less green/blue than when I look at it through the other eye. It’s late and there’s no natural light at the moment so I can’t test it out, but I can always check it out during the day just by closing each eye in turn. I was quite surprised when I first noticed this.

  2. Steve says:

    one eyed colour problems are rare but do occur Sacha. Its possible that you have that.
    Try finding one of the colour blindness tests and doing them with just one eye.

  3. Sacha says:

    It’s definite – my left eye sees things in a slightly more reddish tinge, and my right eye sees things with a slightly more blueish/greenish tinge. It’s not a problem, or at least not a problem I’m aware of!

  4. Sacha says:

    It’s only a slight difference, not noticeable. I was quite surprised when I noticed it.

  5. Daniel Fluck says:

    Very nice article which sums it up very well. I’m also colorblind and I fell myself in the same postion as you are describing here. But I think color blindness does have some impact on every day life, specially when I’m biting into a green banana 🙂

    Sacha, very interesting your one eyed color blindness. And Steve, do you have a source where they write about one eyed color blindness? Would be great to read something about it.

  6. Sacha says:

    A green banana! Actually, I don’t think I’m colour blind in one eye, it’s just that my eyes see slightly different colour schemes. Maybe neurologists could use me as a guinea-pig for experiments… I wonder if this is a common thing?

  7. Steve says:

    From the wikipedia article

    Very few people have been found who have one normal eye and one protanopic eye. These unilateral dichromats report that with only their protanopic eye open, they see wavelengths below the neutral point as blue and those above it as yellow. This is a rare form of color blindness.

    I had a more lengthy description of it somewhere in the info I was going through writing this, but I can’t find it now.

  8. Steve says:

    By the way the people who do really are unilateral dichromates are used in testing colour schemes that are good for the colour blind.

  9. Daniel Fluck says:

    Steve, I haven’t seen this part in the article about color blindness on Wikipedia yet. Thanks for the hint. It sounds certainly very interesting. Almost like a Husky, which has a green and a blue eye 😉

    Sacha have you taken some tests just with one eye? You can find some more tests here – if you like. It would be very interesting to know the results.

  10. Leslie Martin says:

    Hi Sacha –
    I’ve noticed the same thing about my own vision, but with the colours reversed: my left eye sees a white wall with a blue tinge, while my right eye sees it with a yellow tinge.
    I asked a couple of opticians about it recently and neither of them had any idea what I was talking about.
    As I’ve just started searching for information and this was the first place I found something that matches my own experience I thought I’d get in touch.
    So, thanks for posting the article Steve, and Sacha for responding.

  11. mercy says:

    Hi! um… i myself dont have colour blindness, but my boyfriend does. ive always wondered about what it would be like to kno what he sees. i havent ever met anyone who had any kind of colour blindness so it was a little weird , but im used to it by now. OH i wanted to ask, can there be like severe colour blindness? is something that can be really bad or not that bad at all, or is it one of those things where you are or your not? sry so long, hope to get and answer.

  12. Steve says:

    Hi if you get back here. The rate is like 5-10% of the male population so its uncommon but not really rare, so you’ve probably met other colourblind people but not known as its not really obvious unless you find them trying to pick ripe bannanas or something!

    Yes it can effect people to different degrees. Some people are extremely severe and it becomes obvious very early that they are colour blind. Others are like me and moderately bad its also pretty obvious early in life particularly as its hereditary and so family members are often aware of the condition as their fathers/uncles etc had it.

    However some people go through most of their lives and only discover it when they’ve been made to a colour blindness test say for a pilots license.

    So basically it can be a full range, and this is just for the people like me who are missing only one color of three. Some people apparently see only essentially shades of grey but this is very rare.

  13. Middle Man says:

    Being both red-green and blue-violet colour-blind I can fully emphasise. Add to that the fact that I am from Birmingham and, in truth, I haven’t got a lot going for me.

    http://caughtinthemiddleman.wordpress.com/2008/01/16/man-flu/

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