Unfortunately there is some variation between manufacturer's. From Etrailer.com the 7 pin wiring color codes are:
White - ground
Blue - brakes
Red - battery
Yellow - left turn signal
Green - right turn signal
Brown - tail & marker lights
Purple - auxiliary/back up lights
here's a link:
http://www.etrailer.com/faq-wiring.aspx
From RVBasics the color codes are:
White - ground
Blue - brakes
Red - left stop and turn signal
Yellow - auxiliary/backup
Green - tail & marker lights
Brown - right stop and turn signal
Black - battery
http://rvbasics.com/techtips/rv-trav...ug-wiring.html
The center connector should be the auxiliary/backup light, so if your center wire is yellow then most like the RVBasics diagram is correct for you. Particularly since it lists a black vs. purple connnector. At any rate you should verify everything with a meter if possible.
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