Controlling 2-lead, 2-colour LEDs
This should do it. If only A is high then D1 is illuminated via R2. If only B is high then D2 is illuminated via R1. If both are low or high then both LEDs are off. 

You can alter R1 and R2 individually to control the brightness of each color. 







simulate this circuit &ndash; Schematic created using CircuitLab

It's possible it will work acceptably well with a single series resistor and the bipolar LED connected between A and B, but that depends a lot on what actually comes out of the open terminal and I'm not sure about that. Might be worth a try, but try it on a spare LED with something like 10K first. 

Edit: I've added R3 because it's possible A goes negative when B goes positive due to self-generated voltage. And vice-versa.