When I started working Blood Bank fulltime, the institution where I was employed used the different color index cards to match the patients' blood types for the card file! It was rather pretty when checking out histories. We couldn't get it through the secretary's head that AB's are pretty rare and we really didn't need the same number of those cards as the rest. When we got rid of the card file, we had tons of those specific cards. Now I can't remember all of the colors......O = blue, A = yellow, B = pink, and AB = white? Thanks for that memory, Malcolm!