All of the amazing color variations of all mammals (humans included) are combinations of two types of the pigment melanin. Old folks have white hair because if a lack of melanin. Eumelanim is brown to black while phaemelamin is yellow to red. Many animal's hair is not a solid color but is in bands of color along the hair shaft. Many others have an under coat, which may be a different color than the outer long layer, providing even more variation. And criminals beware; all hairs have what are called scales, sort of an artifact of growth like tree rings, and they are as unique to individuals as fingerprints. Believe it or not.