(Typically the flashing lights allowed on non-emergency vehicles are called Amber.) The vaguer the better, I'd say. Amber light, an antenna, black numbers on t

(Typically the flashing lights allowed on non-emergency vehicles are called Amber.) The vaguer the better, I'd say. Amber light, an antenna, black numbers on the tailgate, some reflective tape on the bumper, orange cones in the bed, a clipboard on the seat, and a hi-vis vest hanging in the back window should do the trick.