Color difference

In FIDE Swiss tournaments, where opponents are paired round by round and not everyone must play everyone else, color difference is calculated as games played with White minus games played with Black. If a player has played 3 games with White and 2 with Black, the difference is +1. If the record is 1 with White and 3 with Black, it is -2. Equal numbers give 0.

Only games actually played contribute. An unplayed round adds neither White nor Black. This fits the color history, which preserves the meaningful sequence of colors from games that were actually played even when some rounds had no game.

Color difference does not by itself determine the next color, but it helps establish color preference. In the FIDE Dutch system, for example, +1 creates a strong preference for Black and -1 for White. A difference above +1 or below -1 creates an absolute preference for the color that reduces the imbalance.