I am installing a stereo in my STi, the headunit was a breeze but now I am looking at grey/green red/blue etc. wire combo's in my doors. Does anyone know what color is what polarity?

 

When you look at the plug in the door it looks like a "T"

The wire which goes to the top (horizontal) part of that plug is the negative wire.

 

Thanks,
I used a Fluke meter to test for polarity w/ the stereo on. I would get only 6 to 12 millivolts, but it was consistent so I used that to determine polarity. My speakers sound great and I've read other posts where some chick traced the wires thru and her conclusions are the same as what I came to w/ my multimeter. It certainly would have been easier to use your method however...