The colored part of the eye is called the iris. It controls light levels inside the eye when there is bright light the pupil which is in the center of the iris will constrict (become smaller) when it is darker the pupil opens wide to let in more light.
The iris of your eye is simply a pigment of color that surrounds your eye it is made up of mussels and nerves it is very sensitive and important part of your eye. Go to my.hrw.com and to log in type in bdorin and lifescience in to life science book login. Hope I helped