[jcbc]

FWIW, our experience is with the Allen-Bradley photoelectric sensors is:

Green = No IR reflected (e.g. pointed at carpet)
Yellow = IR reflected (e.g. pointed at gray tape)
Yellow + Orange = Very strong IR reflection (e.g. really reflective material)

We have the white wire of the sensor wired as the signal to a digital I/O on the digital sidecar.

Also, we needed to recalibrate the sensor (turning the sensitivity adjustment knob on the top) when we got the gray gaffer's tape since we had been testing with much more reflective materials before that.