The ring of color called the iris lies just behind the cornea and surrounds the pupil. This colored membrane gives the |eyes| their characteristic color. It is actually composed of minute sphincter (ring-shaped) and dilator muscles, which govern the size of the pupil. Eye color is determined by pigment deposits (yellow-to reddish brown). Blue |eyes| result when the absence of such pigment allows the purplish-black rear surface of the iris to show. Ocassionally a white pigment is present, which causes the iris to appear gray. Newborn babies generally have blue |eyes|, since they do not have much pigment at birth.
