 The term 'colour blindness' covers all sorts of colour vision problems, and does not necessarily mean that the person afflicted cannot see colours at all. Of course, someone with full colour blindness will see the world in shades of grey, but the most common version of this problem causes a person to have difficulty distinguishing red from green. For example, here's a photo, in full colour, and beside it what you would see if you were totally colour blind:   But what does a person see who is only partially colour blind? A problem distinguishing reds from greens is not a very critical disability, but what would you see? A scientist once came up with a novel way of discovering this. He found people with partial colour blindness and asked them to look at a colour photo on a computer screen. Then he showed them a black and white version of the same photo, and had them use the computer's paint/graphics program to colour the B&W version so that it matched what they saw when they looked at the colour version! This is an example of what they produced:  On the left is the original colour version. The right picture, as coloured by the partially colour blind subject, indicates what they see. Colours appear washed out and indistinct. But notice that bright reds and greens are distinguishable; it's the pale colours that are hard to tell apart. The pink flesh of the fingers and the yellow of the cheese are very close to being the same pale geen tint. These colours would be indistinguishable from normally occurring pale greens and yellows! People with this problem have learned not to buy clothing with pale colours, as they wouldn't be able to match colours properly, and might end up wearing one green and one yellow sock. (That used to matter). But generally speaking, this is a minor inconvenience; some people never even discover they have the problem until they're teenagers, and it's certainly less of a problem than other eye difficulties like acute nearsightedness, which is much more widespread. |