I don't think RJ is a specific person. I think RJ is an idea influenced under a few people, or even a larger group of people. Whether that group is under the influence of vizualize, I don't know, but I do know that RJ can't be one single person.

This isn't a theory, but it's something I'm noticing.

Go back through any episodes you care to re-watch, from as far back as you can. Notice how many times you hear the word "visualize," used in conversation, either in interrogation or otherwise.  In the past week I've noticed it twice, once from the episode "Red Badge" (spoken by Roy Carmen) and once in the episode "Red Gold" (spoken by Wes Atwood). 

This can't be a coincidence.  Visualize is a big part of the puzzle, folks.

I think that Lorelei didnt know the real RJ, she thought that Kirkland was RJ because he is RJ's right hand and Kirkland her everytime, probably talkin like he were RJ. It's also posible that he did something similar with Jason. I dont think that the writers will give that obvious clues(the handshake thing and that scene at the hospital)

We all don't know, who actually RJ is but I'm 100% sure that it IS NOT Jane.
Maybe with some special effects they can give Simon Baker(Jane) another role as Jane's twin and he can play a second role at the final chapter. Why a twin(because RedJonh is as clever as Jane)

I apologize for my English but I'm French.

And if Red John was a woman?Erica Flynn (Morena Baccarin) has all the features: brown hair,  age, she is a sociopath. Moreover, we see manipulative, getting everything she wanted, especially among men. For example, we see an episode that CBI Ron offered him tea with a knowing smile.

Finally, if lorelei was not afraid to measure red as red can be john john is not monstrous but physically fine.

Patrick  succumbed to her charme. last words exchanged between pj and erica are "we'll meet again soon."

A theory that surprised everyone but with a big problem. She has appeared very late in the series and starred in Homeland

From the last episode I think RJ is Kirkland cause he's on the inside and his soft baby voice kind of matches RJ's from the episode where he quotes Tiger Tiger and he touch him before he walked away

People i think i might found another clue...
Beside the fact that RJ is most likely a Caucasian male, ~6 feet tall and short hair. There is the 4x13 episode when Rosalind is telling to PJ by phone, that "Roy Tagliaferro" is there with her and you can clearly see RJ's LEFT hand, holding a cup of tea!
On his fingers, there's no marriage ring so "He is Ma..." definitely doesn't mean "he is married". Plus (my opinion), the graciousness of his hand, holding the tea cup, might also suggest that he is English! (and also the "Tyger Tyger" quote).


About Kirkland... i was thinking thees days at another theory: What if Kirkland, like Lorelei, was once an RJ follower and now it's trying to chase him from the "inside"? That could be a reason for the concerns about his cover(?). Please don't send me to hell for this...it is just a thought :)