I told him it wasn't possible, but I've since discovered that I was actually wrong. It's because of a skin disease called alopecia areata. Hair gets its colour from a chemical called melanin, which is pumped in by cells at the base of the hair follicle. As your hair goes grey, these cells at the base stop making melanin. So here's a great truth - there's no such colour as grey hair.
Grey hair is dark hairs, with the newer white hairs mixed in.
This could be caused by a disease called alopecia areata , where your hair, for no apparent reason, simply falls out. Unlike common balding, alopecia areata is just as likely to happen in women as in men. More Homework .