The two color rule was initiated in July 1986, stating that one side of the racket rubber must be red and the other side black. This measure was introduced because of the increased use of "combination" rackets, notably during a European championship game when the winner had used a racket whose sides were both red.
One must note that the surfaces of both sides of a racket may differ, for example, dimpled (pimples) or smooth or even reverse spin. Without the color differentiation, an adversary could not anticipate the serve and likely would lose the game. To enable a player to distinguish between the rubber used by his opposing player, international rules dictate that one side must be red while the other side must be black.