Purple.
Purple Evidence: Purple started out on the launchpad, went up near greenhouse to fake tasks and that's when they passed the Southwest sensor. They successfully faked a task, then went to the balcony to see if anybody was there. There wasn't and they vented to find somebody. They vented from balcony to medbay to locker room to launchpad. That's when they killed...
If that wasn't wrong. It's possible purple didn't see the body. To find the actual killer? Here it is: If brown reported, how did they not pass sensors! They faked the task on the right (Can't remember what it's called) to go "back to finish" in 60 seconds. They waited until nobody was there except one. They killed, vented up to either reactor or greenhouse. They got tired of nobody reported so he vented back to launchpad himself. They vented back to launchpad and reported it himself.
I know they will call me sus, but I at least had a good reason to vote brown off. But hey! That's just a theory a GaMe ThEoRy!!!!!!!!!!!!11111 (that's hopefully confirmed.)