In order for red hair to be created, both parents must have a mutated MC1R gene – the pigment control gene. Typically the MC1R gene converts pheomelanin into eumelanin, which is where dark and light hair are created. The mutation allows pheomelanin to remain, which gives hair the red pigment.
The best looking girl I ever dated had red hair, i blew it big time with her. Still bitter about it.