Well, first of all The Color Purple falls under the broadest genre of fiction. The three primary genres are poetry, drama, and fiction.
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.
Human skin color is determined by melanin, the pigment found in the skin. Melanin is produced by melanocytes which are specialized pigment cells found in the skin. Besides skin color, melanin is also responsible for the colors of the eyes and hair. The production of melanin is triggered by the enzyme, tyrosinase.