I would need to spend $35 and pull the wiring diagram from BMWTIS. Since they changed their SW, I can't get it to work for me at all.
But what I would do if the car were in my bay would be to tune to the white noise between stations, unplug the amp, and see if you still have voltage on those wires. If you do, before re-plugging, use the fader and balance, go full F Rt, and find the set with voltage. Using this method is the only 100% reliable way to find signal wires when we don't have the wiring diagram.
I'm not surprised to find the signal wires to be different colors in a 2011. I am surprised to find the wires to be NOT twisted pair (if that is what you meant).
musicar northwest portland or musicarnw.com
Web site migration complete, still repairing problems. Sorry!