02 sensor Gray Wire??

[BlackSvt2000]

I get my gauges tomarrow, so I decided I do the wiring today to get it out of the way. I wire my af ration gauge to the gray wire on the o2 sensor under the car near the back exchaust manifold. Will this work ok? I heard that the gray wire was the signal wire. I saw to white ones, but neither had the red stripe like use on the front o2 sensor.