Male, 53, Welsh/Scotch-Irish - first grey hair that I noticed was about 32. Didn’t bother me in the least. My mother’s side of the family all had full heads of silver hair and I am following that trend.
It does appear that stress directly affects the process. Just from personal experience.
There are a lot on my chin if I don’t shave for a few days. So far none on my head though. The beard gray started at about 30.
Mid-twenties. My daughter is 24 and she’s been finding them since her teens. Just strays here and there. She freaks out every time, but it never really was a big deal to me. I don’t dye them or pluck them out. Too much effort!
I’m at about 10% gray right now. In the beginning the grays (silver?) grow straight up but eventually they go into a corkscrew curl like the rest of my hairs.
Early 40s. Promptly began coloring, which has turned out to be surprisingly fun.
Honestly, every time I notice how gray I’m getting, I just thank my lucky stars that I’m not balding.
The stylist found my first grey hair when I was 20. My dad started going grey in high school, though, so I was a bit late.
Didn’t bother me much, though I’m about to turn 31 and I’m finally starting to get enough solid grey that I’m getting those cool ‘professor’ streaks on my temples.
I actually rather like my grey. Part of the reason is because I grew up fully expecting to go bald based on the men on my mother’s side of the family. Going into my fourth decade, though, my hair is still thick enough to draw comments when I get it cut. Grandpa died with a full head of white hair, dad’s nearly sixty and not thinning at all, and it looks like I’ll be heading in the same direction.
When I was about 19. I was proud of it: I’d read something that said that early gray hair was the sign of genius.
I do like the look of my gray hair. It used to be a steely gray; now it’s all white.
I was in high school. Thing is, it was just a few random hairs, so it wasn’t like I was graying at the temples or anything like that.
I’m in my 30s now and still have dark hair.
I was about 25.
This was not so much a problem (I’m 43 and still mostly not grey, apart from my hobo beard). The problem was, I didn’t do anything so cool as get distinguished silver temples, or anything like that. No sir, not for me. I got grey BLOTCHES. Luckily, they are on top of my head, and I’m 6’4", so most people don’t see them, but I was sitting down at work one day (in my early thirties), and a woman walking past asked me in all seriousness if I’d spilled paint in my hair.
I think I was 17. Somewhere around there.
I was in college… specifically I think I was sitting in physics class. There might be a causation there.
About 40 years old when I noticed a fair sprinkling of sun-kissed platinum hairs, but thankfully no white or grey ones yet. 
December of 1999. I was about 25. I pulled it out and showed it to my then-boyfriend who laughed at me.
Fall 1991, I would have been about 23. I stared agape at it and then pulled it out and sent it to my love interest at the time. :dubious:
By 18, I had a silver patch at my right temple. At 35, I’ve gone about 1/3 gray.
I saw my first white hair at 26. I didn’t even have the luxury of it being gray. At 27, I have to dye my hair every month to avoid the few white hairs at the scalp.
About two months ago, a few on my temples, at the age of almost 37. When I mentioned this in mock-horror to my wife, she said “Oh, I noticed those ages ago - have you only just seen them?” 
I’ve had a few white beard hairs for as long as I can remember, though. Well, stubble hairs - I’ve never grown a beard.
I don’t remember exactly, probably late 20’s early 30’s.
As long as it doesn’t all fall out I don’t care.
A friend of mine turned completely silver in his early 20’s, he says it’s not silver it’s chrome.
I’m 52, my hair is thinning, but no silver hair yet.
Twenty-four years old and still a virgin. Sheesh.
My grey hairs are actually more very light, mousy brownish-gray color, and I resent them. They drained the color out of my hair and left it blah. I like my actual white/silver hairs. They have cool texture, and they really pick up the light. I look forward to the day I have completely white hair. It’ll look awesome.
In the meantime, I use henna to keep my hair from looking completely washed out.