Question: why do we have different colour hair , eyes, ect?

Ciarán O'Brien answered on 13 Nov 2014:

Melanin!

Melanin is a group of similar chemicals with different colours, and every human has cells that produce it, called melanocytes.

There’s eumelanin, which is black or brown, and is usually found in the skin. If you ever get a sun tan, that’s because the sunlight caused the melanocytes in your skin you make more eumelanin. Some people have skin that always contains lots of eumelanin, while others can only make a bit as a suntan, and others only get little patches of melanin in a sort of spotty pattern that we fall freckles. Eumelanin acts as a natural sunblock to protect your skin from sunburn and skin cancer.

Scientists reckon all humans used to have dark skin because we all originally came from the continent of Africa which gets a lot of sun. Humans who moved to colder, less sunny places didn’t need as much melanin, and over time we lost the ability to make unless the sun was shining.

There’s also pheomelanin, which is pink/red. You find a lot of that produced in your lips and around your eyelids, that’s why they’re so much redder than the rest of you.

Your eye colour is actually very complicated, but melanin is involved. If the cells that make up the iris in your eye produce a lot of eumelanin (the dark pigment), they’ll usually have a brown or amber colour. People with blue or green eyes have more pheomelanin in their iris than eumelanin. But a lot of the colour is generated by other things like the structure of the iris, which is often so fine it can interact with lightwaves.

There’s actually no blue coloured chemical in blue eyes, or any coloured pigment at all! The colour is due to the light being refractred and scattered by the delicate fibres that make up the stroma of your iris..

Combinations of iris structure and different amounts of melanin give people all the different colours of eyes.