In Stewart James in Print, Allan Slaight devotes an entire chapter to variations on the “Miraskill” theme by James and other magicians.
A deck is removed and shuffled.
The mentalist asks the spectator to choose color that will be “his” color, red or black. Let’s assume he chooses “red”. The mentalist writes something on a piece of paper and hands it to someone to watch.
The mentalist instructs the spectator to turn over the cards two at a time making three piles. One will be the red pile if both cards are red. One will be the black pile if both are black. The last will be the discard pile if one is red and one is black.
Once completed, the spectator is asked to count the black pile. Let’s say it comes to 16 cards. He now counts “his” red pile. It may come to 20.
The prediction is opened and reads “You will have four more red cards in your pile than my black pile.”
It can then be repeated with a different result.