The most 'professional' way is to attach an independent 5V power supply to each throttle to determine the wiring arranging. You can just about guarantee the reds will match being the positive side. So simply attach the negative side of your power source to the browns and black (on the guess they are the negative) and check for a voltage rise on the green/orange with a multi meter (earthed to the brown/black) as you twist the throttle.
Now I can hear you thinking, all very good if you have expensive electronic gear. If you keep all your old phone chargers go check them and see if there is a 5V one among them. Simply cut the output plug of the end, strip back a bit of the insulation and fit a couple small alligator clips, and you now have a 5V power source that will prove infinitely invaluable for doing exactly the sort of thing you are wanting to do a typical ebike. A $10 multi meter from a big barn hardware store is sufficient.