Wiring Q - dash lights and ignition from radio?

[GT_Rich]

I am wiring up Autometer oil pressure, water temperature, and tachometer gauges. I would like to simply tap into the wiring that is easy access behind the radio. The previous owner hacked into the stock wiring and did not use a harness, so I'd like to know what colors I need to grab from behind the stock harness for a 12V dimming dash light and 12V ignition switch.

Thanks,