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Comment by 51Cards | Hacker News Reader

Your latter question has always fascinated me as well. How do I know my 'red' is your 'red'. My father was colour blind and I used to enjoy trying to explain the missing colours to him and for him to explain what things looked like. I quickly learned it's hard to describe colours someone else can't see.

I read an interesting article on colour perception once and about how the physiology makes it pretty likely we all perceive 'red' to be 'red'. I will have to try to find it.

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What I find quite ironic is that traffic lights happen to lie right in the centre of the most common form of color blindness: red-green color blindness.

What I find quite ironic is that the UK's effort to combat this problem, by adding a blue tint to their green lights, actually makes it more dangerous for people with my form of colour blindness (protan, which is not the commonest form of red-green blindness but is still significantly represented (2% of males according to Wikipedia)).

That's because having little red vision, at night I mistake cyan ("green") go lights for white street lights. Having street lights suddenly turn to yellow stop lights is unnerving, to say the least.

When I was a kid, in Quebec, traffic lights were color-blind friendly; they used shapes and color and orientation. They arranged the lights horizontally, like this:

   [R] <Y> (G) [R]

For stop, you'd get two red squares. Wait was a yellow diamond usually on the left side, and go was a simple green circle on the right side. If you could only go in a few directions, they'd list them out with green arrows.

Seemed like a great system to me but I don't see it in use as much any more. Perhaps it was too expensive to manufacture custom lights for just one province.

you're talking about qualia: http://en.wikipedia.org/wiki/Qualia#The_inverted_spectrum_ar...

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