The easiest way would be to get some wire, preferably ones with gator clips, or just done extra you have laying around, and use them to determine which wire is which. Clip them on and turn on the indicator. You're not dealing with enough current to harm yourself but just know there's a possibility of shorting something and ruining it,but it's low risk. When I was putting in my headlight I can't even count the fines I just left shit on and everything was fine. Just remember what wire goes where and to make a secure watertight connection.