There may be other wires going up to the roof. If the red and black are 10 ga or so, they probably feed your solar panel. The 12V feed is on the computer board and should be black and may have a 18-22 ga black wire attached. The ground will be white and right next to it on the board....
My fans worked intermittently so I simply went up on the roof, removed the vent cover and put 4 muffin fans up there and wired them direct. I made a metal box for them to fit into and screwed it in the opening in the roof. Very efficient and works like a charm. To access your fans, the fridge must be pulled forward far enough to get up and work behind it. That seemed like a pretty big hassle compared to adding the extra fans. My fridge had two and now I have 4 130cfm ea. up there....Dennis