What year W126? FSM says blue with red stripe for 83, blue for 84-85.

I don't see speaker wires in that jumble. You're looking for a black/black and green pair and a black/black and red pair. They go as far as the fader thumbwheel by the shifter then split to the front and rear speakers.

The brown wire with blue stripe and spring clip connector is the trip wire for the security system. Suggests your car is '85 or later.

Sixto
87 300D