What colored part of the human eye controls how much light passes through the pupil?

Until roughly 11,000 years ago all humans, like great apes, had only brown (darker to lighter) irises. Then apparently a genetic mutation occurred which generated variant colors in only approximately 8% of all humans.

Iris is the only 'colored part of eye that light passes through' innit or does the other answers allow light

Jeorne, We just need cats eyes! lol

It would be terrific if we invented spectacles that could work like the eye lens.

Until approximately 11,000