i don't really have an specific idea who Red John may be because i think the show is purposely trying to mislead us into thinking that certain people who have popped up are red john
clearly they are not going to make it as obvious as someone who the viewer may suspect although they could make it so obvious that we actually just ignore them to being red john
i think whoever red john is, when Patrick has met them they seem the least likely to be a killer
Red john isn't going to act suspicious around Patrick because he wouldn't want to get caught so he can carry on with his game.
it's annoying as my theories change all the time
i thought that maybe it's Patrick himself but i don't think they would make the 'hero' the killer.
i feel like Van pelt may be connected as we never really get to know her that well and she does seem like shes hiding something.