You don't say which model Taco, but on my 05 DC, the L rear speaker leads are Black & Yellow, and the R rear leads are Red & White. I tapped into mine under the rear door sills, just remove the screws & it pulls up. For testing the wires, I use a volt meter & safety pins. Just stab the pins thru the insulation then connect the volt meter. If it is not the correct wire, a little tape or liquid insulation covers the tiny hole. Oh yeah, make sure that you have a good ground to the sub.