Just a thought...Heller said that in the last scene of the first episode of the sixt season "There is a clue buried in that final sequence that will pay off big time
in the finale of the Red John story. A very big clue. No one will get
it from the clue as it is laid out in the episode, but it will pay off
later".
I've watched the finale scene a lot of times and couldn't notice nothing strange.
Then I thought that the clue maybe wasn't a "thing" but a "behavior".
In this context I noticed one thing strange: the way RJ painted the smile on Lisbon's face.
When he finishes painting the smile seems to caress her cheek.
Can this be the clue?
RJ is someone in love with lisbon or someone very close to her (maybe a member of her family)?
I don't know if this is important but is the only thing that seemed strange to me.