Wiring diagram for 1967 Plymouth AM/FM radio

It has 4 wires.

Two pairs of two.

IIRC a pink and yellow, and another harness with a blue and brown?

Not finding anything in my wiring schematics or online.

I'm assuming the wires are

1) back light
2) radio power
3) one speaker
4) the other speaker

But I have no clue which is which. Any help is appreciated. Thanks. Eric L