#1010, "RE: covnerting trailer lights from 4-flat to 5-flat" In response to In response to 0
Rob , The color code goes like this.......
White = ground brown = tail lites/marker lites green = right hand turn signal yellow= left turn signal
The fifth wire (blue) is typically tied to your back up lights circuit and its purpose is to disable the boat trailer's "surge brakes" when backing up. If its a big boat with electric brakes requiring a "Brake controller" then the blue wire could be used for the output from the controller . You need to first determine if the blue wire is used for trailer braking .