I was told by gas company person that their crews use only pipe dope on threaded connections, and never use teflon tape. It was not a sealability issue, but rather a debris issue in that, improperly installed, a fleck of teflon tape could blow through the line, and potential clog a jet.
I have no chemistry credentials, but I do not think teflon tape will brake down in the presence of LP, or any other heating gas. The different colors of tape available only serve to visually indicate the thickness of tape.
But hopefully, there might be a Chem E in Minnetonka with better info