Several genes control hair colour. All these genes affect the amount and type of pigment in your hair, but some have stronger effects than others. It is possible for two brown-haired parents to have red-haired children. In the parents, the effect of their brown-hair genes masks the red-hair gene, but they may still pass on a red-hair gene to their children. Any child who gets two red-hair genes (and no brown-hair genes) will have red hair.