Yes, your pubic hair may one day turn grey just like the rest of the hair on your body. It will turn grey for the same reason the hair on your head turns grey, extreme fright, just kidding. The colour of your hair is determined by its pigment. Eventually you will lose that pigment and your hair will turn grey, although it’s not really turning grey, really its dark hair and colourless hair and the contrast between them that makes hair look grey. Someone with no pigment at all has white hair, when you pull a ‘grey’ hair out of your head, or other places, you’re really pulling a white hair out.