How to Identify Aftermarket Car Stereo Wire Colors The reason you usually don't actually need a wiring diagram to install a car stereo, even if it's a second-hand unit that didn't come with any paperwork, is that aftermarket car stereo wire colors are actually pretty uniform. Unlike OEM head units, Related searches for gm radio wire diagram gm stereo wiring harness diagramgm wiring color chartgm wiring diagram wire colorsgm delco radio wiring diagramgm stereo wiring diagramgm radio wiring color codegm speaker wire colorschevy factory radio wiring diagram