Update from the UK Haynes W124 manual -

Here are some wire color codes to help you:

- blue = antenna power lead
- red with white stripe = always hot
- black with yellow stripe = hot when key switch is on
- gray with violer stripe = hot when lights are on (not dimmer)
- brown = ground

It doesn't describe the speaker wire pairs as left or right.

Sixto
95 S420
87 300SDL