The sticker on the MMPro case also has ABC markings (under the PCB where the motor wires are located). If that sticker is missing, you can try googling a pic of the MMPro to see where they would be.
EDIT: Here's one:
http://i1018.photobucket.com/albums/...MonsterPro.jpg
If you cannot view the image, the red wire is A, white wire is B, and black wire is C.