Attempt Number: 4
Error Message: The action and resulting child state have already been explored.

Action Reasoning:
The last action taken was a move by robot1 from tile_1-3 to tile_1-4. According to the instructions, if the last action was a move, the next action should be to change the color of the paint gun exactly once. Currently, robot1 is holding black paint. Since we need to alternate colors according to the goal state and the next unpainted tile above (tile_0-4) should be black, changing the color to white at this point is necessary for future steps. However, to keep the sequence intact, we need to first change color as per the immediate next action rule.

New State Description:
Robot1, holding a white paint gun, is still on tile_1-4, which remains occupied by the robot. The tile_0-4 is not yet painted.

Action Chosen:
change-color(robot1, black, white)
