Human skin color within a "fair/medium/olive" context. Oculocutaneous albinism (OCA) is a lack of pigment in the eyes, skin and sometimes hair that occurs in a very small fraction of the population. The four known types of "OCA" are caused by mutations in the "TYR", "OCA2", "TYRP1", and "SLC45A2" genes. In hominids, the parts of the body not covered with hair, like the face and the back of the hands, start out pale in infants and turn darker as the skin is exposed to more sun. All human babies are born pale, regardless of what their adult color will be. In humans, melanin
Biological pigment that are within the photosynthetic structure are more common, but complicated. Pigment-protein complexes that are outside of the photosynthetic system are less common, but have a simpler structure. For example, there are only two of these blue astaxanthin-proteins in the jellyfish, "Velella velella", contains only about 100 carotenoids per complex. A common carotenoid in animals is astaxanthin, which gives off a purple-blue and green pigment. Astaxanthin’s color is formed by creating complexes with proteins in a certain order. For example, the crustochrin has approximately 20 astaxanthin molecules bonded with protein. When the complexes interact by exciton-exciton interaction, it lowers the