Eli5: What’s the biological reason behind humans having eyes(irises) of different color?

Question

I know that eye color is directly related to the amount of melanin present in the front layers of the iris. But what’s the biological need behind different color?

In: 98

Answer 1

You tend to see more diversity in eye color in places where skin has less melanin. There is good reason for melanin reduction in skin…it enhances vitamin d production in areas without much UV light. I suspect lighter eyes are just a side effect of selection for lighter skin.