This is a very easy to fix. All you need to do is reverse the positions of the wires between the motor and controller.
To do this unplug the motor from the controller. Then take a very small screwdriver and one at a time push the locking tab of the terminal pin flat with the pin and gently pull the pins out of the white plastic connector. Then restore the original positions of the terminal locking tabs using the same screwdriver and push the terminal pins back into the plastic connector in the opposite positions that they were in when they were pulled out. I recommend marking the position of either the red or black wire with a permanent marker or tape so their original positions are not forgotten after the terminals are removed from the connector.