[denisond3]

I dont know anything about the changing of colors, but to connect the voltmeter you want a ground - most anything under the dash that is metal should do to bolt to, and a 12 volt connection that comes on with the ignition. Usually these can be found on the fuse block, and you add a wire from a fuse for someting like the radio, running to the voltmeter.
I dont think auto voltmeters are very accurate, and each one may read a little high or low. But usually they will give a good repeatable idea of whether you voltage is getting too low, or too high.