People have been commenting on my grey hair since I was 15 years old, and whilst I did go through a phase of disliking it, I actually think grey looks very cool, and most other people I meet seem to as well.
Mind you, maybe I'm lucky in that my hair is dark silvery grey (has black in it). I'm 28 now, so I've had greying hair for a good 13 years. No complaints at all, wouldn't have had it any other way. I feel lucky!
To answer your question though, I have heard Propecia can sometimes slow down greying or reverse some grey in some people. Actually that's one of the reasons I am put off.