Check my gallery pics - my chin dirt is almost completely gray - or rather, there's pure white hairs mixed in with the rest of the colors in my beard, raning from pitch black to bright red - but they are mostly concentrated in my moustache and wrapping around my chin. It's really noticable in direct sunlight, and I have to say I've gotten more comments on the colors in my beard than any of my other public features. Probably because I try not to shave much - when I do (like I had to for my corporate job, but I still kept the chin dirt), I get a lot of ingrown hairs that cause problems.
I can't do it as I have these two spots on either side of my mouth that don't fill in well, but whe I try to do a van dyke-style goatee, it's almost completely gray and I've been asked if I've dyed it that way.
I've got some silver coming in at the temples too, and I've found gray hairs on/around my nads, and on my chest.
It's been weird, as even though I'm the black sheep of my family, I've got the lightest hair color, I'm the only one who'd balding, and I'm the only male with any premature graying going on. My sister has a reverse Jay Leno thing happening with jet black hair with a gray patch at her widow's peak, but she can work it and it looks good.