THANK GOD IT ISN'T GALE BERTRAM.

If Stiles is really dead, I can't see Red John being one of any of the other seven suspects; Heller compared, regularly, Jane to Sherlock Holmes and Red John to Moriarty. 
Both Bertram and Smith are in on it, that much is obvious, but Red John? Heller's representation of the ultimate good is Patrick Jane, in that the death of his family caused him to see the world with abnormal clarity; Red John is not, as many suppose, Jane's polar opposite, but rather someone just as clever and charismatic, just driven (possibly even by similar motives) to a different end, that of evil.
Red John would not hide this charisma and intelligence as Heller would have us believe Bertram or Smith do. He would glorify in it, rather like Bret Stiles, and would take pleasure from mental jousting with Jane. However, Stiles is dead, and even if he weren't, I'm not so sure that he is Red John. Someone linked to Visualize, but who has a similar history as Jane in the Carny industry would be the ultimate Red John in my opinion. Red John is still pulling the strings, somewhere, watching Jane and laughing at him.  
But all will be revealed in episode eight, I suppose... just please do your brilliant story justice Heller, and make RJ the Moriarty we've all been hoping for.

Let me help you guys and girls. :)

Red Herring

Remember the interview of the alleged Red John. He said he was surprised because he thought he was just a red herring.

Interview with Lisbon
The Mentalist's Robin Tunney(Teresa Lisbon) has revealed she was "surprised" when she found out the true identity of Red John. https://tinyurl.com/mhzcd5d

Interview with Brett Partridge
Let’s say you turn out to be Red John, is there something about your character that you would've liked to incorporate from the get go, or are you fine with not having known the whole time?
Jack Plotnick(Brett Partridge): Well, I played it like I was Red John from the beginning.
https://tinyurl.com/kqoxga4

Remember nobody knew who was playing Red John in the cast until a few weeks ago.

There are several theories here, and Bruno Heller has thrown out so much clues that almost anybody could be Red John. Just so much clues, every viewer could see it the way he wants it to be. Everyone has his or hers own Red John.

SUSPECTS Characteristics:

Gale Bertram 
100% a Red Herring, just to distract the viewers.
He is scared to get caught.
Steals probably Thomas McAllister's stuff in his vault, the woman looked at the name card Thomas.
Killed a bartender without drawing a Red John face.
He loves the poems of Blake
Is a member of the Blake Association.
He always talks on the phone to someone higher than him.
He felt scared when Reede Smith was angry at him on episode 2.

Sheriff Thomas McAllister: One of my favourites.
Has a ring
Classy shoes,
Good gun aim(season 2 final and episode 3 saving Jane on the roof),
Plays mini games with Jane, Rock paper scissors, guessing the victim is a pizza guy.
Gets irritated when he loses Rock paper scissors with Jane. https://tinyurl.com/msndqrp https://tinyurl.com/kwvc43u
Bertram goes in a wine vault with the name Thomas. Wine is made in Napa valley.
Xander Berkeley has the talent to act like a plain normal sheriff of a small village, and he could change it to a very intelligent narcissistic serial killer. https://tinyurl.com/k3tefwj
Quite an expensive actor.
Red John needed FBI to get information, he is not from the FBI.
Hates pigeons.
Partridge is a pigeon, he could have killed him with hate.
Calls Patrick Jane by his first name like Red John.
Doesn't make sound in the woods.
He likes to hunt anything with a face.
Fits the description of Rosalind Harker, he was younger when he was with her.
This episode 6x08 promo picture possible RJ escape, he is shot and just look at him.
https://tinyurl.com/nz7tz8t
Calls Teresa Lisbon also by her first name.
Probably dead.
Could have brought the bomb in his hat. He had put it on the couch.
Has a charming relaxing voice.

Reede Smith
He confessed.
He said Red John needed his FBI skills to receive some information.
He gets scared when someone possibly CBI Ron is whistling in the hallway.
He is just a guy who killed a young girl and he wanted to get out of trouble, that's why he used the help of the Blake Association.

Bob Kirkland
Allegedly a good guy
Wanted to catch Red John, because RJ killed his brother Michael.
Got killed by Reede Smith.
He had a lovely high pitched voice though.
He loved to talk in a relaxed manner with Teresa.
Killed Jason Lennon and asked do you recognize me?

Ray Haffner
Is in love with Teresa.
Is scared by Spiders.
Has a security company.
Fits the description of Rosalind Harker. 
He is too emotional.
He wants to save van Pelt en Teresa by warning them.
He comes to the hospital bed of Teresa after a nurse has checked if Jane is there or not.
Has a charming appearance and voice.
Is a member of Visualize.
Has no tattoo.
Doesn't like Jane that much.
Worked at the CBI.
He lifts weights.
Didn't want to answer Teresa about a certain Red John case, we're still friends right?
Probably dead.
Has filmed with Bret Stiles before the Mentalist https://tinyurl.com/l483opf

Bret Stiles
Has probably the most resources of all suspects.
He is the boss of the cult Visualize.
Has a lot of followers.
Has blood rituals and draws it on faces.
Charming voice and appearance.
He really likes Patrick Jane.
Calls Patrick his boy.
Helped Patrick to let Lorelei escape.
Says he knows Red John.
Immediately when Patrick saws the 3 dots on Thomas McAllister, Bret told Patrick that Reede and Bertram have it too. 
He has a terminal illness.
Probably dead.
Has filmed with Ray Haffner before the Mentalist https://tinyurl.com/l483opf

Brett Partridge
Appeared in episode 1, and says Red John enters here.
Somehow is intrigued by Red John's work.
Says the Red John killings are fake when it is real and vice versa.
Says Lorelei doesn't count as one of Red John's victims.
Patrick Jane doesn't feel comfortable with the guy.
Got allegedly killed by Red John.
He is a forensic expert.
Has the perfect high pitched voice.
Been called a ghoul by Patrick. The definition is a gravedigger.
Somehow shows he is scared for Patrick.
The body's left shoulder is cut off. It could be a fake body of a Blake Association member and he just cut off the 3 dots to make it like he is dead.
The actor said he always played like he was Red John.
He has the most believers to be Red John on the planet.
Said TygerTyger to Teresa maybe as a help call.
The voice in the season 2 final saying the TygerTyger poem resembles his voice.

CBI Ron
Biggest troll of the show.
Probably is the whistler that scared the living hell out of Reede Smith
Works for the CBI
Saw Bertram escaping from the hospital and said Hey Boss.
Has a high pitched voice.
Has probably the most cameo appearances of the show.
Probably a Red Herring that got popular by the fans and Bruno Heller likes to use him now.

I hope this long list makes a lot of things more clear. I have certainly forgot a lot of things, that I will regret when I have posted this online. But I am also human. Let's make this post reach the top.

Cheers.

Question: why do people here believe every quote Bruno heller gives is true?

He has said RJ was one of the seven suspects when asked. If RJ is not one of the seven what answer do you give to that...? "No he's not on the list, just skip the first 7 episodes and watch the reveal"?

At the end of the day heller will be judged on the plot, not his honesty in interviews.
It's in his best interests to misdirect us every way he can.