factory wiring cut, install help please!

Hi

My car stereo was cut out of 99 Mustang, I checked here on the forum and the wiring diagram for the 99 mustang doesn't seem correct when I look in the dash.  The color's don't match up..Anybody know how I can use a multimeter to test all of the wires and find out which one's are which.  Power and ground are pretty easy, but how about speaker leads..

Any other ideas would be great too..

Thanks

/Davide

I don’t have the diagram at the dash other then the power. But here is how the power in the dash should be, as well as the speaker wires after the factory amp. Is this a Mach 460 or standard radio? You might also want to try the bottom diagram here http://www.installdr.com/Harnesses/Ford-Wiring.pdf

|        RADIO 12V|lt. GREEN/ violet    |   |at the radio                |