Chevy & GMC Vans

Hi! New (to me) Astro owner, new to this site. I just bought a 2000 astro awd with the factory delco stereo and speakers (6.5" in rear doors and 4x6 in rear pillars). the front door speakers sound good, but the ones in the rear doors distort from the bass. I would like to tap into the rear door speaker wire, behind the plastic trim covering the drivers side wheel well, to install bass blockers, as well as connect a powered subwoofer tube. Until I can get a shop manual, can anyone tell me what the factory color codes are for the rear speakers ( after the factory amp by the rear wheel well).
thanks!

Here is a photo of my drivers side rear dutch door wiring attached to a new speaker - I am not sure if you can make out the strip on the wiring - but this might help. I'll find out exactly once I am at home tonight and post again then.

Drivers Side Dutch Door Speaker Wiring

Okay just got home - here's what I have for wiring in my 2001

Drivers Side Rear Dutch Door - Green with Black Stripe & Blue with White Stripe

Passenger Side Rear Dutch Door - Solid Green & Blue with Black Stripe

As far as which wire is positive/negative to ensure your speakers are phased correctly is a mystery to me at this point - I'll figure it out eventually - probably after I replace every speaker in the van. But for my current project it won't matter one I install the aftermarket amp and 6 x 9's

Cheers

thanks. MY subwoofer connects to the left and right positive only, and it has a phase switch, so I guess it doesn't matter if they are transposed. But it will not put out any sound if it is not connected to both positive wires. I plan to tap into the wires behind the plastic trim between the drivers side rear wheel well and the rear a/c. there is a loom of several wires there, and I want to be sure that I tap into the correct ones to avoid making a hack job out of it.