A similar thing happened to a friend who was over for game night. We were playing the Monopoly Deal card game when he put a brown and a red card next to each other with kind of a confused silence. Look at this:
https://static.wixstatic.com/media/374991_dc4dfa2a6f0d4ebb81...
(Pictured: Three red property cards next to two brown property cards.) They use only color to indicate property group. I was surprised that such a recognizable brand would allow this to get through. About one in twelve men cannot play this game without assistance.