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.
Skin color is determined by a pigment (melanin) made by specialized cells in the skin (melanocytes). The amount and type of melanin determines a person's skin color. Melanin gives color to the skin, hair, and iris of the eyes. Levels of melanin depend on race and amount of sunlight exposure. Sun exposure increases melanin production to protect the skin against harmful UV (ultraviolet) rays. In addition, hormonal changes can affect melanin production.