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.
Hair Colors. Red, yellow, pink, green, orange, purple, blue. Hair color is one of the most easily identifiable traits of an individual. The color and style of a person's hair is one of the first things the brain uses to identify who we are seeing. (This is why we tend to confuse people who have similar hair styles and color). Because of this, hair color is often used in media to distinguish different characters.