Definitely a Crewmate

Green ended up finding Heracles in the tank, despite their love to kill they're not going to kill a fucking fish and besides it'll be easy to kill the crew without sabotaging O2.

While heading back to the group... after dealing with the body of Lime, they bumped into the weapons seat and a wristband dropped, they picked it up, put it on- don't ask me how, and now they can hear you.

I think Green was an imposter the entire time and Orange was infected.

I know it's a pretty popular and...well easy to contradict theory for Orange to have been an imposter the entire time despite them saying they loved salt.

But it makes more sense for Green to have been other than the "only one broken ore+ and one of the imposter larvae being seen" and the first part? The worms. Green is obsessed with worms, even when their act dropped they specifically said that Orange "couldn't kill a sunbaked worm" The imposters look similar to worms in their true forms (other than the shapes they take), the same stereotypical pink and slime and overall tendrils.

If Green's worm farm was actually a nursery for eggs that would make more sense. As well as Green outright saying they hated competition...the worm farm could have just been the same planet where the reactor incident happened or an entirely different one FULL of crewmates. It was stated nobody died on that incident so it would make sense for there being some abandoned crew and the possibility for the imposters to eat the remaining population and compete for food.