2005 chevrolet silverado with xm

i have 2005 chevrolet silverado with a factory deck and xm built in. I am trying to wire in an amp and sub but i am unable to find the color of the rear speaker wire. Everything i have found so far has told me L/R speaker +/- BROWN / Yellow and R/R speaker +/- Dark Blue/Light Blue, but i only have brown and dark blue. No yellow or light blue, any one who can help i would appreciate it thank you

Your truck will have an amp in the bottom of the center console. The larger plug has your rear speaker wires in it and they are the dark brown, yellow, dark blue and light blue. You can get to them by pulling the storage compartment and the console lid off.sparky

thank you i will try that and let you know what i find.