I've noticed no difference in potency the major difference will be color, yield will definitely be reduced by cold temperatures as it's slowing the plants metabolism substantially, especially if it gets too cold in flower. Cold slows or locks the sugars up in the plant to my understanding and cold sugar doesn't flow well.
If you want to crank the colors I would let the plants just about finish within a week then crank your AC down to 62 °F for a few nights before harvest, should help bring out the purples.
