I was talking to someone today after having wowed them with a few card tricks

basically the magician shows the backs of the cards to the spectator one at a time and asks them if they think it is black or red, they then put them into two piles depending on what the spectator says -
and when the spectator picks the cards up at the end they find they were correct.
Well, thats how I was told it went.
Any ideas what this is called - and if it is a gimmicked deck or just a straight card trick? (£50 says Seige
