T-bone

I replased factroy radio with a new one. I have all the wires hooked up and now my dash lights don't work. I had 4 plugs that hooked up the the old radio. I use 2 for the speakers, 1 for hot ,ground and switch. Now the plug has a black , gray and yellow wire. I hooked the black to the ground, yellow to battery, and gray to red. Now the dash lights stay on. I took the gray off and the lights go off. Tryed to hook it other places and the lights stay on. Where did I go wrong??