Looking at the schematic for the combo switch it's a mess - it appears to be digital sending pulses of a certain duration to the BCM which are then converted to voltages which feed the IPDM (intellegent power distribution module) under the hood. THe IPDM outputs 55 and 56 are from the highbeam relays and are color coded G (green) and L (Blue).
(see pages LT-53 and LT-8)