As is clearly stated in the match rules, the colors reverse after game 6 to allow both players the same number of games (potentially) as White after a rest day. Topalov, having White in each even-numbered game during the first half of the match (Games 1-6), now reverts to having White in each odd-numbered game during the second have of the match (Games 7-12).
This results in the oddity, due to the forfeit of Kramnik as White in Game 5, of Topalov having the White pieces 3 consecutive games in a row: G4, G6, G7.
Needless to say it is critical for Kramnik to hold this game, effectively neutralizing the advantage of Topalov with the White pieces.
G7: Topalov,V (2813) - Kramnik,V (2743) [D27]
WCh Elista RUS (7), 04.10.2006
(Thanks to Mark Crowther, The Week In Chess, and Malcolm Pein for commentary and analysis)
1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.e3 e6 5.Bd3 dxc4 6.Bxc4 c5 7.0-0 a6 8.Bb3 cxd4 9.exd4 Nc6 10.Nc3 Be7 11.Re1 0-0 Diagram