I believe that the NHTSA or some such government agency did a study (many years ago) and found yellow to be the most visible color -- which explains why highway crews typically wear yellow.

I've got a red/white/blue tricolor jersey which seems to get noticed - motorists give me wider berth and often beep horns for the colors of the flag. 'Course, if they understood that it is a French National Team jersey, some of them would probably run me over.