Hair color is determined by two different forms of pigment: eumelanin (which is the largest influence) and phenomelanin. Eumelanin is a black pigment, and phenomelanin is a red or yellow pigment. Hair color is determined by three factors having to do with pigments: how much pigment is present, to what degree a eumelanin or phenomelanin is present and how close together the melanin (pigment) granules are. The more eumelanin a person has, the darker his hair will be.