If both parents have a blue and brown gene, their eyes are brown, but if the child inherits the blue gene from each parent then the child will have blue eyes. If the child only inherits one blue gene then they will have brown eyes.There are two layers to the iris, the anterior and the external, or front and back layers. To produce blue eyes, there is no pigment found in the front layer. The brown pigment melanin is deposited in the back layer only. It appears blue because of reflection and diffraction of light. In green eyes, a small amount of melanin is deposited in the front layer of the iris along with the melanin found in the back layer. The additional pigment to the amount needed for blue eyes, causes the eye to appear green. To produce gray eyes, the dark pigment is distributed in the front layer of the iris and over the blue background it appears gray. In brown eyes there is so much pigment in the front layer, that the blue behind is completely covered up. Some people have so much pigment in the front layer that their eyes appear very dark brown or black. Hazel, blue-green, gray-blue eye colors are produced by different amounts of pigmentation and the pattern in which the pigment is placed. Albino eyes are have no pigment at all in either layer of the iris. The iris appears pink or red because of the reflection of blood vessels in the back of the eye. The pattern in which the pigment is deposited is also determined by genetics. The pigment may be deposited in rings, clouds, radial stripes, or spread over the entire iris.
