Color history

A color history records, in order, which color a player had in earlier games. It can be written compactly with W for White and B for Black. FIDE also uses u for an unplayed round in examples from its pairing rules.

When a color sequence matters, FIDE counts only games that were actually played. An unplayed round does not break the meaningful sequence. For example, BWBuW, with round four unplayed, is treated as uBWBW when recent colors are evaluated: the games actually played are effectively grouped at the end.

Color history helps determine color preference, because Swiss pairing systems try to avoid excessive runs of the same color. It is different from color difference, which is only a number: games with White minus games with Black.