If two different types of rubber coatings are used in manufacturing a ping pong paddle then such a paddle has two different sides and ITTF has made this rule to make one side red and the other side black. Two different types of rubber coatings are used to give players more variety of shots. The color difference is created to help the opponent in understanding which side the player is using. By looking at the color the opponent can know whether the player is going to play offensive or defensive.