what is the responsible for the colors of the human eyes?

Answer 1

The cones are photoreceptors of Color Perception. These are 1 of 2 photoreceptors located in the retina. FYI: http://www.answers.com/topic/cone-cell-1?cat=health

Answer 2

The pigment in the iris and the choroid layer of the eye is what gives colour to it.

The iris has a hole or aperture in it to allow light to reach retina, this hole is called pupil.

If you look into someone's eyes, you will see a disc surrounding a hole (pupil) that disc is iris and that is what gives the eye its colour. The pupil always appears black.