Hmm that might be possible. I don't really think it's necessary for the game at all, but it's kind of a fun Crossfire event. Right now I've got all my cards covered in cheap penny sleeves that are completely transparent. They're thin, which helps with shuffling and such. I might be able to find some similar sleeves that are opaque on one side, ideally colored. If they're completely opaque and all look the same, it's hard to verify which pile they go into.