I need help decoding 1998 CRV speaker wiring
 

Both front speakers have the same color wires. Blue and gray/black
The passenger side rear has red/yellow and brown/white wires.
The driver's side rear has gray/white and blue/yellow wires.

Which ones are the + wires?

There is a spare connector taped to the driver side rear speakers. What
is that used for?

Thanks for the info.