i just bought a pioneer deh 3400 deck from my friend and he did not have the instruction manual my question is what color wires on the pioneers harness go to what sets of speakers?

 

Easiest thing to do is buy a gm aftermarked radio plug. You can get them at wal-mart or any car audio shop. That plug will wire up color for color on the plug coming out the back of the radio and the aftermarket plug will plug into the factory plugs in the car. It makes things a lot easier doing it this way than trying to hard wire it into the car. Hopefully you still have the factory plugs in the car and you didn't cut them out.

 

Unfortunately the previous owner cut the factory plug off thanks any ways

 

As Gambit said get the quick harness for GM vehicles and match them up, You can also get the replacement harness for the car and just wire it in.
Here is a helpful site that will show what color to match up to your car.
Here is the page for your manual. Just scroll to the middle for yours.
You may have to register to get the manual, but its 's free, just download and print, PDF file.