The Install Doctor - Radio Wire Harness and Colors - Chevy Free car stereo and car radio installation resource. Step by step installation instructions complete with photos, tool list, and wiring detail. What Is the Color Diagram of a GM Radio Wire Harness wwwrence›Car Parts & MaintenanceThe General Motors GM radio wire harness uses gray, orange, yellow, pink and black colors. The color scheme is generally standard for vehicles of every year. Continue Reading.