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

In addition to what everyone else has said, it’s also possible that eye color is a sexually attractive trait. If females of a species are more attracted to certain traits, that trait will increase in the population, regardless of its biological benefit.