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.
The darker a person's natural hair color is, the more individual hair follicles they have on their scalp. Levels of melanin can vary over time causing a person's hair color to change, and it is possible to have hair follicles of more than one color on the same person. Particular hair colors are associated with ethnic groups. Gray or white hair is associated with age.