Wrong-colored bishop
A wrong-colored bishop runs on the opposite color to the queening square of its side's rook pawn, so it can never cover that corner or drive out a defending king sitting there, and the ending is drawn.
The phrase describes the bishop, not the pawn, and it matters most when you are deciding whether to simplify. With a rook pawn, the winning plan is to promote on a corner square, so the bishop has to be able to cover that corner. Use a quick test: note the color of the promotion square, then the color your bishop runs on. If they match, king, bishop and pawn normally win; if they differ, the bishop is wrong-colored and a defending king that reaches the corner draws. The bishop can never check the king there or take the corner square away, so the remaining tries either give stalemate or let the pawn fall, as the example shows. The wrong bishop still has work to do before the king arrives. It can guard the squares the defending king needs on its way to the corner, and if those squares stay covered, the ending is won after all. When attacking, look for a way to keep a second pawn on another file, or trade into a structure where your bishop matches the queening square. When defending, aim to exchange pieces and pawns until only the rook pawn and the wrong bishop remain, then head straight for the corner.
Compare it with Bishop and knight checkmate. Bishop and knight checkmate is the ending in which a king, a bishop and a knight force mate against a lone king, which must be driven into a corner of the bishop's color.
It sits close to Wrong rook pawn. A wrong rook pawn is an a-pawn or h-pawn whose promotion square is the opposite color to its side's bishop, so king, bishop and pawn cannot win once the defending king reaches the corner in front of it.
If "Wrong-colored bishop" has cost you half a point, a first lesson is a good place to find the pattern behind it: George Li goes through your games and builds a plan.
Related terms
A wrong rook pawn is an a-pawn or h-pawn whose promotion square is the opposite color to its side's bishop, so king, bishop and pawn cannot win once the defending king reaches the corner in front of it.
A rook pawn is a pawn on the a-file or the h-file, the edge of the board, which has fewer capture options and gives the attacker less room to maneuver.
Stalemate is a draw that occurs when the side on move has no legal move at all while its king is not attacked, so the game ends on the spot with half a point to each player.
A fortress is a position the weaker side can hold indefinitely: its king, pieces and pawns cover every entry route, so the side with extra material has nothing to aim at and the game ends in a draw.
A minor piece endgame is an ending in which each side has only bishops or knights besides the kings and pawns, so the fight turns on piece activity, pawn structure and king position rather than on heavy pieces.
Guides that go further
What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.
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A game review, a read on your level and a written study plan from George Li.
Want to spot this in your own games?
A first lesson starts with your games: George reviews them and builds a study plan around what he finds.