|This is another form of sliding block puzzles.
The board can easily be drawn (each cell is a square) and the pieces can be counters or coins. The usual rules apply. There is no passing or jumping, and only one piece at a time may be in any cell of the board.
In this case all you have to do is -
Exchange the positions of the RED and BLUE counters.
This puzzle was invented by Henry Dudeney, the great English puzzlist, in about 1910.
It has been produced many times since then in various forms - often using themes like parking cars or manoeuvring space craft.