Different Manufacturers make their cables in different ways. There are a number of different combinations that can be had, however the most common is having the motors rotate in the wrong direction. 

When Homing, the chameleon should spin the cam in the CLOCKWISE motion. If spinning anticlockwise, the motor cables will need to be reversed. 

To reverse the motor cable, they will need to be de-pinned and then re-pinned in reverse. The easiest way to do this is to de-pin the selector and extruder cables individually, and then reverse the order of the cables in each connector.

For example, my cable is wired from left to right with the following order:

RED BLUE GREEN BLACK

If your motors spin in the wrong direction, just take the cables out of yours and wire it in the reverse order to how you bought it. So mine will end up being:
BLACK GREEN BLUE RED

Depinning the cables can sometimes be a tricky process so take your time. A pick is a good tool for this task.