Hello,
To be honest, there just aren't a whole lot of GMC's out there, so I haven't had much opportunity to look them over closely. I really don't know if they had different colors, but since they always had a little "better" product, it's certainly feasible. GMC had a tendency to use new products before the Chevy truck division even heard about it. BTW, I did see your other post and went here to direct you to it.
What you are probably going to have to do is start off with the colors listed above as a guide, and use a jumper wire to confirm what goes where in your application. There isn't anything that can get hurt by your putting power in any of the harness wires, but of course use a fused jumper regardless.
If your turn signals aren't working, there are several things that might be wrong.
1. the brake light bulbs are not connected right. That means they could be either not getting power, OR THE GROUND SIDE ISN'T CONNECTED. I had to run a jumper on my pickup to connect the bed to the frame, due to poor electrical contact on the frame mounts. If the brake lights work, then the ground is OK.
2. the T/S switch is bad
3. the flasher is junk. Your harness wire that comes from the flasher should be hot all the time with the ignition on.
4. the fuse feeding the flasher is bad. Always check barrel fuses by using a test light at the side clips in the fuse block, NOT by touching it to the fuse. Corrosion on the clips keeps electricity from coming out of the fuse and into the harness. Make sure and test this while the T/S switch is engaged, so there is a load across the fuse.
Give it a try and get back if you still need some help.
------------------
David
newbie #4153
