I found out when my parents sent me to Catholic school when I was about six or seven. Unlike public schools where we brought our own crayons to school and they had paper labels on them, this class had thick communal unlabeled crayons which we all shared. I colored my skies purple and my grass brown and the nuns thought I was a discipline problem until it was discovered I was color-blind by the school nurse. (FYI, I *was* a discipline problem also)
When I was in the Marine Corps, I happened to be walking through the mall one day and saw a table full of marked-down jeans at The Gap in Cardiff-by-the-Sea, CA. That was in the 80s when colored jeans were fashionable. I didn't want colored jeans though, just blue ones. I found a stack of them at $6 each and bought 4 pair of them. They were indeed purple and not blue, as I was laughingly informed back at the barracks.