I have an old Kenwood cmos -230 backup camera from some rig I sold.   Id like to throw it on my trailer, but I don't have the complete harness.  Only the pig tail off the camera.  It's discontinued and I can't find a harness anywhere.  4 wires,   red,  black, green and yellow.  I assume red-power, black- ground. Just not sure about green and yellow.  I believe those would be wired into the rca plug, just not sure which is which.  Any of you car electric experts know?  

if the color coding is universal, the yellow is video and green is the backup lights would trigger the camera to turn on.
but I would think that might need to be in the head unit, not the camera itself.

Ya my kenwood head unit has a purple wire that you hook to the reverse circuit.  It tells it to switch to the camera when in reverse.  You can hook the red wire to the back up lights so the camera gets power when they illuminate.  The other 2 coming from the camera usually wire into a rca plug that runs to the head unit.  Only thing I'm not sure about is which wire goes to the center post and which goes to the outer ring of the rca plug.

I dont recall the whole color codes on these but I do know that yellow is video sigal. I had to track down a broken wire on a chevy truck one time and google gave me which color I needed to trace to find it.