need help finding a/c compressor wires on 85 GMC

[72farmer]

I have a 85 GMC Sierra Classic.I am going to try to get the a/c going.I can't seem to find the wire going to the compressor.The compressor has 2 wire terminals on it.I thought most older vehicles that had a/c on them only had 1 wire to compressor.The negitive ground was done through engine ground and mount.

I need to know what color wire or wires would come from pressure switch and go to the compressor.