I believe, on my F150, the black wire was the one for the trailer battery feed, and blue one was for the brakes. The tag on the harness says it's a Ford.
http://www.f150-forums.com/attachments/1997-2003-ford-f150-7/48d1303303854-trailer-wiring-excursion-related-ugg-7waytrailerend-jpg
is a link to a picture of the correct colors to function. Good luck!
2020 Torque T314 Toy Hauler Travel Trailer- 38' tip to tip.
2015 F-350 6.7L Diesel, SRW.
2021 Can Am Defender 6 seater. Barely fits in the toy hauler!