Anyone installed an A/F ratio gauge before?

I could spend hours looking at wiring diagrams, but i thought i'd post here first. anyone done this before? I have to connect a violet wire to the wiring harness. The o2 sensors have a 4 wire plug of various colors. one is supposed to be a ground, two are for the o2 heaters and the last one is a signal wire --i think! (i need to tap into the signal wire) The signal wire on the gauge is Violet and there is a violet wire on the o2 wiring harness. Is it humanly possible that GM or autometer would make something so simple that the violet wire on the harness would match the violet wire on the gauge? does anyone know?

 

Wonders will never cease, huh? It's the violet.