Since no one has had any comments, I will put in my 2 cents. I put fog
lights on my '03 Silverado and found that the wiring harness is
different for one built with fog lights at the factory. It has the
correct plugs routed to the lights. The harness without fog lights
didn't have them. I went to a junk yard and found one with the correct
harness and instead of buying the harness, I just looked how wires were
run and bought the plugs at Pep Boys and wired them up. Also, I had to
have the computer programmed to turn them on with the correct switch. I
think they charged me $20 at the dealership for that.
I have no idea if this relates to your Colorado.