Ladies hat colours
Three intelligent women, Alice, Barbara and Carol, sit down to try out a test in logical reasoning. They are arranged so that each can see each others hat, which is either red or green, but none of them can see her own hat. They are told that at least one of the hats is red. If any one of them can logically deduce the colour of her hat, she is to declare it immediately. Carol alone decides to play this game with her eyes closed. After a little time Carol, correctly declares her hat colour. What is Carol’s hat colour (and why)?