Like Rookie, I've heard dodgy things about chestnuts.
Its not always crazy, but in the stories they always have attiude, temper, or are nuts.
I'm sure its purely coincidence but I think every chestnut I've ever met has had one of these. Rosie, my mare, is a chestnut and she has a real personality and attitude about her, and she's just at the beginning of the list.
Compared to bay horses (my faves!) who, while not neccisarily dull or anything, seem to be more stable and amiable in my experience.
I wouldn't turn a horse down because of their colour (thats a lie - i'd probably turn down a grey but for practical reasons) but I'm not 100% convinced that colour doesn't influence it in some way.
I've also heard Appaloosa's are crazy but I think its just because of their eyes (you generally see the whites more), and not because of their personalities.