I'm purchasing a trailer to tow with the van.  The trailer has a 4 wire inline plug labelled: white=ground, Brown= taillights, Yellow= left turn and stop, Green= right turn and stop.
In other words the turn signals and brake lights are on a shared connection. 
The Westie has separate wires for each turn signal and the brake light, which means a 5 wire connection.
The question is: Do I have to change the trailer lights, or is there a way to hook up this combination.
Thanks in advance.  I don't post very often but am a faithful reader and learn a lot from all you experts.

Ed Wiebe