I have had a light blue contrast collar shirt with both a white collar and cuffs for a little while now. I picked up another one thrifting today that was so cheap I bought it even though the collar was only white and the cuffs were the same color as the shirt. This one was also light blue. I wouldn't wear them often enough to keep both so I'm going to sell one. My question is, is it a "faux pas" to have a contrast shirt with only the collar being white, or does such a rule not exist?