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
Respiratory pigment Respiratory pigment A respiratory pigment is a molecule, such as hemoglobin in humans and other vertebrates, that increases the oxygen-carrying capacity of the blood. The four most common invertebrate respiratory pigments are hemoglobin, hemocyanin, hemerythrin and chlorocruorin. Hemoglobin is bright red when oxygenated, and dark red(purplish) when deoxygenated, oxygenated hemocyanin is blue in colour, deoxygenated it is almost colourless. Oxygenated chlorocruorin turns from green to red, whereas oxygenated hemerythrin is a violet to pink colour and colourless when deoxygenated. Any of various coloured conjugated proteins, such as hemoglobin, occur in living organisms and function in oxygen transfer in cellular respiration.