The colored part of the eye is called the iris. It is a thin, round, highly pigmented circular membrane between the cornea and the lens that divides the eye’s anterior chamber into an anterior and posterior chamber. The iris has a center opening called the pupil, which is surrounded by muscles that can narrow or widen it to regulate the amount of light reaching the retina. The color of the iris depends on the pattern and amount of melanin, a dark brown pigment that the iris contains. Dark brown eyes contain the most melanin, while lighter eye colors, such as blue and gray, contain only a little.