First: sorry for my English ... I don't know who is Red John but is very interesting the girls with red hair: Van Pelt, Rosalind, Frye, Hightower ... I think Red John are these girls, Ron o Brett Partridge.

I think that Red John is a group of people, not just a single character; "he" is a terrorist group with a common goal.

Haha this is a very very interesting setup Bruno has us all working and scratching our heads about. I chose someone else because I believe that Bruno has yet to show us Red John. Gale Bertram would be my guess for the person in CBI working with R.J. But I doubt that he is R.J. When things tensed up he looked to out of control for RJ. While in the episode that Jane came the closest, RJ was sipping on some tea. None of the other tea drinkers are really good options for RJ. RJ is someone much higher up, someone with more influence and power than the usual subjects. The man he had killed in Mexico? That was pretty quick... No doubt RJ has someone in the CBI, but Gale and the others are not the right caliber for RJ.  

Patrick Jane Has been put under hypnosis for the whole duration of the series by someone, the word used is roll tide it was done to jane in the last episode of season 2 he gets tapped on the shoulder twice. The same hypnosis was done to other characters throughout the show like kristina frye and that waiter in the last episode of season 2  
. I think hypnosis word he uses is roll tide.

I am new here and wanted to share my thoughts on who it is, and is not. Huge fan of the show and I am also a writer.

IS RED JOHN A WOMAN?

I tend to doubt this for several reasons mainly that Heller in every interview refers to John as a man. If he used the words Red John when talking about the character, instead of "he" etc. I would buy into it being Kristina. However he said at the end of the day Red John is just a man...and that we might have seem HIM already.

Is Red John Patrick Jane?

Lot's of reason's to think so...great theory and the concept would rock. Jane could have multiple personalities..The Tiger Tiger is all about opposites, and good vs evil, two sides of the coin per say. Patrick has a way with people, he can sort of control them...and so does Red John however, the major problem I have with Patrick being Red John? There are so many people involved there is no way they could convincingly sell it as Jane being split and being both. Heller is too smart to screw this up like that. It has to be someone else.

Red John is small and pettitte...so we can rule out anyone large and tall like Bertram.

Could it be Hightower? Worst theory ever. Makes zero sense, sorry.

Rigsby or Cho? Again, no sense.

Stiles? I just don't see it.

Here is my theory...Red John is someone that is smart but obscure and always has been. However, he is someone that has been around. We may not have always seen him.

My theory as of right now is that it's Ellis Mars

Reason? He is an astronomer. Tiger Tiger has astronomical references. "Roll Tide" is an astronomical event. The Red Face? The Planet Mars (also is last name) has a red face with eyes and a mouth. He is one of the few that has been involved in a Red John case and he is still alive. The writing on the wall "He IS Mar"...perhaps the IS is not  an "i" and an "s" but an L and an S making it "he LS Mar"...Mars is the Red planet. He is one of the few involved in a Red John episode that did not claim to know Red John at the end. He LOOKS harmless (soft). He knew Jane would scoff at him and not take him seriously because of his "gift" so he felt safe. Correct me if I am wrong but didn't Ellis Mars business card have a tiger on it?

I think Red John is either Walter Mashburn or Kristina Frye. I am hedging toward the former for the following reasons. He is smart, well educated and seeks thrills as normal life leaves him bored. He has the resources to do what Red John does, and significantly, unlike many men of his wealth and status, Walter is self deprecating to the point where he wants you to think he is just a bored, pampered playboy who likes playing games but is no real threat.

Despite this Mashburn is likeable and yet despicable. I think he is good for it. He is also enigmatic enough to be RJ. JJ Larouche and Bertram have potential to be followers of RJ but not RJ themselves. Brett Stiles gets off on controlling people not murdering them.

Kristina could be RJ as she is a little too goody two shoes for her job description and it never was quite explained what has happened/likely to have happened to her. In any case I hope RJ;s identity is done well and does not turn to be really crass  -like be someone like Lisbon.

RJ should be consistent and believable with what the story has told us so far while at the same time leaving room for surprise, but not shock.

I think Red John is Patricks father, because he knows Patrick very well he is every time one step ahead. And Pareick left him.

Or it is Steiner.