please help! need cd player install help!!

ok here's my problem.....i have a 89 s-10 blazer and i bought a pioneer deck for it.....the dumbass who had the truck before me cut off the factory wire harness to install a tape player.....in the back of my cd player is a red, black, and yellow wire.....i hooked the red and black wires to their spot and can't find anything for the yellow and my cd player will not turn on with the red and black ones in.....so can someone please help me?? thankx in advance.

see if these will help

http://www.installdr.com/Harnesses/GM-Wiring.pdf - wire guide

http://www.installdr.com/InstallDocs/GM/PDF/460037.pdf - installation guide