A person’s skin pigment, which determines hair color and skin tone, is influenced by the melanocortin-1 (MC1R) gene receptor. For the population’s 1 to 2 percent of redheads, a mutation in MC1R accounts for their red hair color and typical light skin.
http://hms.harvard.edu/news/how-red-hair-may-increase-melanoma-risk-8-22-13