always bored

When the number of crewmates have been whittled down to four, Red still tries to reach out to Purple and states that they still trust them. Mind you at this point Purple would've had a 1 in 4 chance of being an imposter. I also noticed that at no point does Red ever accuse Purple of being an imposter, they might have some suspicion as to why Purple was never at cams during the murders, but they never lead Red to directly suspecting them.

I believe that deep down, Red knew what they did in the past by sucking up to Mira was wrong, and their trust in Purple is an expression of their acknowledgement that Purple was always the more principled of the two and someone they could rely on.