I haven't had a chance to observe homozygous/heterozygous grays to much. I can tell you from personal experience though.
BLACK Gray Mare (MFT I think) - Started to show noticeable lighting in the face and body by five. She got progressively lighter, but 'gray gray' didn't start showing up until about five years old.
BLACK Gray Colt - Son to the mare. Noticeable graying by two years, born true black.
BLACK AND WHITE TOBIANO Gray Colt - Son of the black colt, by a black Tobiano filly. Noticeable graying by one year old, he pretty much showed real graying after he shed his baby coat. Born black and white Tobiano.
September '10. He turns two in March I believe.
Unfortunately, no baby pictures :( I have a few pics of his dam, but none of his sire or granddam. I think his grandsire is Dusty, sire of my Loki and Redman. Not sure though, I'll have to check when I pick him up. He's been gelded, so theres no telling how fast his offspring would gray out
It kind of frustrates me though, because nearly everything you read on the internet says they get these white "goggles" around their eyes, like that is always the FIRST place to gray out, and look for, if they are a gray.
I have decided that my colt is in fact turning gray, even though he doesn't have goggles. He has lots of sprinkling on the bridge of his nose like your guy. And white hair sprinkled throughout his coat. But still no major noticeable white hair around his eyes.
So why does everyone insist they must have "goggles" when they don't all gray out in that fashion? Isn't that kind of misleading to someone who is trying to figure out if their colt is a gray?
I suppose there is a chance my colt could not be gray, but if he isn't, he's a funny looking roan.