What is the Factory Wiring Harness Color Code for a 2007 Brown - Tail Lights. White - Ground. Light Green - Backup Lights. Blue - Electric Brakes. Red/Black - 12 Volt Power. We had a 2007 Chevy Silverado with the factory trailer wiring on our lot, so I went out and verified that it had the same color code. I also noticed a white tag on the wiring harness that listed the functions of each wire color. TRAILER WIRING INFORMATION - iegtoclub GM trailer wiring code. A white wire may also be found in that bundle, it is a brake light wire which is not normally used for trailer wiring. Dodge tow vehicles with the Factory Tow Package Brake Connector Dodge vehicles with this package are equipped with a 15 amp fused power line which is insufficient for 3 & 4 axle (6 or 8 brake) applications.