The YELLOW JERSEY style/wannabe/race leader discussion notwithstanding, studies done a number of years ago indicate that riders (both bicycle and motorcycle) wearing bright yellow tops and helmets were significantly more visable to motorists and were less likely to be involved in auto/cycle incidents.

I always wear a yellow shirt when I ride - I want people to be able to easily spot me when I crash in ditch or by the side of the road.

Dean