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

Evolutionarily, adaptations don’t arise because they’re necessary. They arise randomly and persist if they, at minimum, don’t significantly interfere with an individual’s ability to have offspring. There’s not significant advantage to any particular eye color, they’re diverse because they don’t really make a difference.