Dear Kevin

Colour vision in primates (humans, gorillas, chimpanzees, monkeys, etc) probably evolved with the foods that they ate--especially fruit.

If a ripe banana is yellow then it might be easier to see for a hungry animal that will eat it and spread its seeds in the process. And the hungry animal would need to be able to see the colour yellow to identify the fruit.

Berries and other fruit are often red when they are ripe. Again, they can more easily be seen from a distance if they are red (like red traffic lights) rather than green. If an animal finds them and eats them then later on the seeds will be excreted and they may grow into new berry bushes. Then again, a spider might be coloured red to advertise how poisonous it is.

So having colours and being able to see colours is useful for some living things. The world is colour-coded for the animals and plants that need it.

Perhaps that's why carnivorous mammals don't need colour vision--they make their own Vitamin C and don't have to go and get it from fresh fruit and vegies. Likewise for grazing animals like horses and cattle.

But I don't think I have answered your question.

Do you mean why does yellow look yellow and not blue?

The easy answer is to say that different parts of the visual cortex (in the brain) are excited by the different colours.

But that doesn't explain the sense of what the colour is that you hold in your mind.

I'm afraid no one has been able to fully explain that yet. Some people say it is a mystery and we never will be able to explain it.

Some one else might say that there is a problem with your question. Although it seems to make sense it may in fact be meaningless.

Conscious experience is conscious experience. For me, yellow is yellow and blue is blue.

Yours sincerely 

Virginia R. Claire

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