Brown. Green is right blinker and right brake light,yellow is left blinker and left brake light.Ground is thru trailer frame. That's for a flat 4 wire connector,the white wire can be ground,but is generally not used.
I am still curious why Tony actually has possession of the trailer.... but we are in 20 degrees and snow guessing at the color. Next time tell him to get out and look.
The funny thing is that I was a low voltage system designer for a while, ran commercial sound systems, tied directly into 240 (hot) all the time, built distros, was a lineman for the cable company and did underground and aerial line splicing.
But hey.... anything to make the phone not ring.