The gregorys manual should be correct but if in doubt here is what I do...and I'm s'posed to be a Master Installer!
The colours will be in pairs...a light green and a dark green etc etc....
Using a AA battery out of the TV remote, hook the two wire upto it (with the deck disconnected) if they are speaker wires, you will a speaker pop....listen for which one it is. As for the polarity....Hook up a left and right...if there isn't much bass, swap them around and there should be more bass. If it's less....put them back to how they were. Do the same with front and back. Then once all four are hooked up play around with the fader and balance control. The bass should DECREASE as you take power away from one speaker. If you find it starts increasing as you remove power from one speaker completly, then that speaker is out of phase.
!_WARNING_! When using the battery, just touch the wires onto the end. Do not hold it there for long periods of time. If by chance you are able to see the speakers, pay attention to which way the cone moves, if you can work out which configuration makes the speaker go a certain way then you will have worked out the polarity of the speaker wires at the same time.
