Reverse switch for EB3XX controller

[Tyro65]

I believe I have an Infineon controller EB3XX. I'm not 100% sure, since I can no longer read the model number on the unit. It runs fine. It controls an old Crystalyte front hub motor. I've been trying to rig up a reverse switch. I've tried a dpdt switch to reverse the polarity, trying all possible combinations of the yellow, green and blue phase wires: Y with B, Y with G, B with G to no avail.

I welcome suggestions on how to do it.

Thanks.