"My 15 year old son during trick or treat. What is he dressed as, you ask? He is a Sheild Agent, he wasn't collecting candy, he was handing out cards to all the kids dressed as Marvel characters asking them if they were interested in the Avengers initiative."
Not everyone. My one-quarter Cherokee mother's hair didn't start showing gray until she was 68, and I have a 72 year-old redheaded friend who still has no gray at all. Even at 95 my mother's hair was still more pepper than salt.
I have friends who started gray in Jr high, and were fully gray by 23. I started gray at 22, and have full sideburns at 35, so who are YOU to DECIDE when it's appropriate to accept gray hair?