On my dometic in an A126 the red and green are for 12v and 120v operation (never have both on at the same time!). There is a separate thermostat knob lower on the unit toward the bottom for gas. On mine set it to off when no lp is needed or to the desired cooling level and light the pilot when Needing to use lp.
Yours may differ so post up the year of your camper and hopefully someone with experience on that model will chime in.
2011 FR Rockwood Premiere A126 Hard Side
TV=2011 Jeep Wrangler Sahara 2 Dr
Reese 66065 WDH, Curt WDH Shank #17120
Prodigy P2 Brake Controller, Mopar 7-pin Harness
B&M Transmission Cooler (#70268)