Consider this: final vote scene, but with Imp! Purple instead of green.
Green had the evidences this time. As an intern with work load so big it make them run around the ship multiple times a day, they began to notice how Purple changed their tastebud. How purple began to be near storage more, near the ore+ that they discovered to be alien eggs and yada yada. And also how they had let multiple crews die on their watch. And they were actually BELIEVING that Red would believe them and vote Purple out, because they genuinely looked up to Red as a mentor and captain (despite Red being the biggest chud loser ever).
And Purple were at a disadvantage because they had no way to disprove Green's evidence.
But right as Red were about to give their vote, "Purple" use the same expression as when they were begging Red not to sign the NDA. They began to dangle the illusion of their forgiveness. Used the scraps of their memories of the time the real Purple spent with Red to nostalgic bait the captain. And then ever so innocently, they started guilt tripping the captain, reminding Red all the mistakes that they made. And dropped the final bomb: despite all their mistakes, "Purple" still believe that Red could change. And they could live and be happy together...
And Red, driven by guilt and all their feelings towards Purple, voted for Green. And right as Green was begging Red to reconsider, "Purple" shifted into their full alien form and killed Green right in front of Red. It was quick, but Green's remains scattered everywhere, and even on Red's face, like a reminder for the captain that yet another innocent life had perished right under their nose.
I LOVE YOU, MANIPULATIVE PURPLE.
God, can I gush about that final voting? Bcos it really was just. So good. Red having to put their trust in Purple into action. Purple admitting they don't have evidence like Greem, but Red, if our friendship ever meant anything to you, now is the time to prove it.
For that genuine moment of self-reflection and humility, to be taken advantage of, bcos the thing pretending to be Red's Purple knew just enough to know how badly Red wanted this. A chance to do right by Purple.
And it ends with a kid dead.
The thing is, Purple really could have just killed them both. But I do like the interpretation that since Crewmates are social creatures and the Impostors who take them over assimilate and mimic most Crewmate behaviors, they prioritize getting along with others over their killing instincts. And the game makes it more satisfying.
Purple didn't NEED Red's vote. If Red voted for Green, Purple could have rampaged against them like Green did in canon. But the pleasure was in knowing Red still loved Purple enough to choose them this time.