According to Pachman, the value of the Bishop can usually be assessed by the following rule:
The Bishop has good working power if its own pawns are posted on squares of the opposite color, assuming that the pawn formation cannot easily be altered.
As a rule, each side will try to place their pawns on a color opposite of that of his Bishop; this makes it easier to block the opponent’s pawn on squares accessible to the Bishop. When the position has become simplified and the pawn formation fairly rigid, both sides will try to rid themselves of a bad Bishop and keep a good one.
