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

There isn’t really a need for it. People with blue eyes have better night vision and worse vision in bright light, because more gets through their iris, but it’s not really needed.

Evolution is kind of random, some traits exist not because they’re useful, but because they’re not harmful enough to be bred out by selection.