Help! Need to I.D. wires for rear speakers, 87 Carrera

[movin]

I hope someone can help me. I found the wires to the rear speakers near the head unit (I'm changing it). The problem I have is trying to determine which color is rear left(+) and rear left(-), and rear right(+) and rear right(-). I forgot to label them when I cut away the old head unit.
Second question is how can I verify if the rear speakers are wired correctly (to the right color, in-phase, not reversed polarity)? The problem here is I don't seem to be able to access the rear speakers at all, so I can't see how their hooked-up. The rears are some old ADS two-way enclosers and I can find no way the pop the covers, they're on like permanet. Is there an easy method for checking a speaker's wired polarity?
Thanks a bunch!

[jbrinkley]

I *think* red for right, whatever other color is left
I think red/brown - and red +..... you get the idea
touch wires to a 9 v battery to be sure, if you can see the cone check phase that way, they will pop when you touch the battery with them.