I am not sure who RED JOHN is but I very sure that HE is NOT KRISTINA FRYE. WATCH the last episode in SEASON 2 - Red Sky In The Morning.

In the event where PJ was saved by Red John from the two insane students, you can listen to his voice. Though RJ may sound feminine, he definitely sounds like a MAN. Now when he mentioned "Roll Tide", which in the event was the one that Kristina Frye said to the waiter in the start of the show, it was actually because HE WAS LISTENING TO THEM WHILE THEY WERE DATING. Look closely at the scene and shots when PJ and KF were talking to the waiter, during the time before she mentioned "Roll Tide", you can see a man wearing a black suit on the table next to them. He has black straight hair. You would see that in the left side of the screen, near Jane. He was actually interested in ROLL TIDE because the waiter mentioned the phrase "CRIMSON Tide" where his uncle belonged to. CRIMSON, a shade of RED. You can check the episode, see for yourself. Kristina Frye is not RED JOHN.