Steve is right, blue would be a single wire for the rear speaker. Pic is not great, but that looks like a double wire, and probably someone added an aftermarket rear speaker.
well the thing that surprises me is that it goes under the factory sound proofing.... could it possibly be the original wire?
If it's a 2 lead wire, it's doubtful it's factory. The factory didn't put things under the soundproofing unless they were protected by a plastic channel or wrapping, cuz' they could short out. Someone probably just lifted the soundproofing and stuck the wire under figuring it would be protected maybe. Does it have, or look like it had a rr speaker?
