Coloring problems are scenarios in which the colors of depicted units, whether Black or White, are unknown. The objective is to determine the colors of these units, ensuring that the resulting arrangement is permissible. These types of problems were first introduced by A. K. Kniest, who explored the topic in an article published in “Diagramme und Figuren” in 1964.
A nice example of such a coloring problem was created by G. Husserl in 1986:
The position is almost impossible to reach because both kings cannot be in check simultaneously. The only way to explain this situation is that the queen has just promoted from a pawn, so the king on g7 must be black and facing a discovered double check.
What if we move the rook to g7?
The solution would be based on the same principle (pawn promotion) but still a bit different:
In addition to the basic coloring problems, there exists a plethora of more intricate variants. These advanced versions often involve a substantial quantity of pawns and major pieces, contributing to the complexity of finding a solution. I might discuss these elaborate coloring problems at a later point.