You neglected to tell us how many "systems" you have in your camper.
One system would be the outside lighting
- - Stop/Turn-Clearance/Tail - - On a 4 wire system the "normal" convention for these lights is
Brown wire to the tail or parking lights
Green wire to right turn signal/stoplight
Yellow wire to the left turn signal/stoplight
White wire to common or chassis ground
A second system would be trailer brakes
3rd system would be interior low voltage lighting
(12 volts). Usually a battery
with a current limiting device. Examples would be a circuit breaker or fuse. At a minimum you will need a "hot" wire and a ground wire for the return path. The battery
is probably connected to the same ground as the trailer lights. You may have a wire from the tug to the trailer for charging the battery
4th 120 volt house lighting
with an external cord to a campsite supply. (shore power in boating parlance)
Many times people have installed spare wires for future use or abandoned wires from removed equipment. It is usually a good idea to mark the orphan wires and tape them on the ends even when they are not used. I use white electricians tape and a fine point sharpie pen to mark wires as I identify them. Not because I can't figure it out but because my memory is shot.
I think you get the idea. You have to separate systems - Then the identity of the wires in the camper start making sense. If you have any questions after you identify what you have we can sort it out.