I see a lot of street people whose gray hair looks yellowish instead of whiteish. Why is that?
The answer might surprise you: hardwater. Hardwater and hair don't usually get along, and after enough exposure to minerals and metals (like calcium, magnesium, aluminum, copper, manganese, and iron) it can turn yellow.
Okay, but that doesn't really seem like it would be the main culprit to me.
Chlorine and other chemical residues in water, sunlight, and even oils from the scalp can also give gray or white hair a yellowish cast, says David H. Kingsley, PhD, a hair and scalp specialist in New York City.
(Thanks "Doc." I'd think the last two factors would be the more likely guilty parties.)