system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do eyes have that awesome pattern around the pupil and what is the purpose of the coloring?
gpt
The colored part is called an iris and is a muscle used to control the size of our pupil, the black part of our eye that allows light to enter. 

The color is caused by a mutation that reduces the amount of melanin contained in the iris, this lack of melanin allows light to be reflected out of the iris in hues of blue or green and different shades of brown.