Number One Trick
This trick dates back to around the 70s. The magician asks a viewer to make a number plate with red numbers on one side and black numbers 1-9 on the other. Place it on the table in the color you choose with the face up.
Once selected, grab the board full of circles and place it on the number board to completely cover it. After the magician turns back, he asks the viewer to say a number from 1 to 9. The magician will then be able to tell the chosen number in red or black.