<P> Red hair ranges from light strawberry blond shades to titian, copper and less commonly "true" red . It is caused by a variation in the Mc1r gene and is recessive . Red hair has the highest amounts of pheomelanin, around 67%, and usually low levels of eumelanin . At 1--2% of the population, it is the least common hair color in the world . It is most prominently found in the British Isles . Scotland has the highest proportion of redheads; 13 percent of the population has red hair and approximately 40 percent carries the recessive redhead gene . </P> <P> Gray or white hair--sometimes colloquially called "salt and pepper" when it is' peppered' throughout dark hair--is not caused by a true gray or white pigment, but is due to a lack of pigmentation and melanin . The clear hairs appear as gray or white because of the way light is reflected from the hairs . Gray hair color typically occurs naturally as people age (see Aging or achromotrichia below). For some people this can happen at a very young age, even as young as 10 . </P> <P> In some cases, gray hair may be caused by thyroid deficiencies, Waardenburg syndrome or a vitamin B deficiency . At some point in the human life cycle, cells that are located in the base of the hair's follicles slow, and eventually stop producing pigment . Piebaldism is a rare autosomal dominant disorder of melanocyte development, which may cause a congenital white forelock . </P> <P> Caucasian people often begin to grow gray hairs in their mid-thirties while Asian people begin graying in their late thirties, but most African people retain their original hair color until their mid-forties . </P>

Why does red hair get darker with age