Have 4 prong trailer plug with 5 wires how to hook up extra wire

All colors will hook up the same, however that last wire probably blue, will not go to anything, that is for trailer brakes, if your vehicle isn't equiped with a controller then dont' worry about it, other wise you can always buy adapters from just about anywhere even home depot or walmart

The 4 prong plug will have 5 wires attached to it.
The white wire is the ground and is attached to the trailer frame near the front. There will be two brown wires and one goes down each side of the trailer. These wires will have a connection at the side marker lights near the front of the fenders. They will then continue to the tail lights. The light bar in the center is also connected to the brown wire.
The yellow wire at the plug is for the left stoplight and the green is for the right stoplight. One of the wires out of the taillights will be brown and the other wire will not match the color of the harness wire.