Don't quite understand the question, but, the colored wires are normally the "hot" wires while the white wire would be the ground... There are also installations where the socket is self grounding there is only wire and it will be "hot". The bulb itself is unidirectional, it will glow no matter how inserted as long as it fits into the socket. Some of the LED replacement bulbs are polarity dependent and will not work if the bulb is inserted "backwards", but, can be made to work if taken out, rotated 180 degrees and re-inserted.
By and large, trailers are wired much more like a house and not so much like a vehicle. Colored wires will more than likely be "hot" and white will be ground...as opposed to green and that is because 12v circuits don't require a neutral.
My 2 cents, your mileage may vary...
2 Cats; J-Lo and Ragamuffin :R
2014 Thor Tuscany 40RX DP
2011 Ram 2500 Longhorn CTD HO
2011 Keystone Cougar 318SAB (now gone)
2008 FunFinder X 210WBS (Sadly gone)