2003 Gmc Seirra

I need some help on figuring out the wiring  for the door speakers on my truck i am installing new menphis speekers in the door and i need to know what is positive and negative thank you very much

When you buy the proper adapter, it will be labeled----no reason to cut up the factory wiring.

Or, use a small battery to test the factory speaker.  If the battery makes the speaker pop out toward you, then + from the battery is the + speaker wire..................... if the speaker pushes in away from you, the battery's + wire is conneced to the speaker's - wire.