Robert Kirkland.

First appears in the 100th episode - at the end of the episode, directing an FBI agent to call Minelli, warning him about Patrick and asking for regular updates about the Red John case.
In If It Bleeds, It Leads, he meets Patrick and Lisbon for the first time. The mispronounciation of Lisbon seemed deliberate, as if he was trying to conceal having followed her team for years. Bumping into Jane was definitely deliberate - I suspect he may have slipped something into Jane's pocket or taken something out, its was a classic pickpocket maneuver, or maybe just engineered for them to 'meet'. He says 'sorry Mr Jane', Jane says, 'do I know you?' and "Bob" responds with, "No, but I know you" as they shake hands. He also matches what we know of the physical description of Red John.

He's in another episode too but that hasn't been shown here yet.

I suspect ultimately he wont turn out to be Red John, the way he's been presented is too obvious but I think we're supposed to believe for now that he's Red John. He may turn out to be the Red John associate of the season.

Bruno Heller said that Red John isn't going to be some mid-range actor. IMO at this point, it could only be Brett Stiles, unless he means its going to be some unknown actor.