I prefer darker briefs. But I also enjoy wearing multiple colors as well. For me, Underwear is sexy and fun. I hate white briefs though, so difficult to keep pristine over a long period.
Based on my own personal observation in the gym lockerroom, most men I see wear a type of black/dark blue underwear. I always wondered why black was so popular for underwear when black is supposed to make things appear smaller. On the flip side there are quite a few that wear white or gray. The guys that get the most attention are those that wear bright colors like red, yellow, etc. Most of the guys wearing jockstraps seem to prefer white.