Have been thinking this through, probably more than I should, and this is what I came up with so far:

1) It is Bret Stiles' long "lost" partner from back in the day when they were putting Visualize together. I think that Stiles himself tried to end the menace called Red John in the early days by attempting to kill him, but failed to do so.
Why? -In the beginning of season 5 we saw what probably is the first act of Red John - the killing of 2 Visualize members, which have set him on a revenge course against his buddy Stiles. Now, once he was almost caught in the basement with the bodies (the daughter of the vet said that she thought someone was watching them there) he realized that he cannot do what he's set out to do by himself, therefore recruiting men and women willing to join his cause. Then he realized that the "petty" dream of chasing his arch enemy was nothing compared to what he can now accomplish with the army of people he amassed (practically gaining the same thing Bret stripped him of), he gave up on chasing Stiles and devoted himself to do the one thing that fulfills him the most - kill.
Most likely suspect: Sheriff McAllister. If my "memory palace" is as good as i think it is, someone informed Jane that Bret's partner was killed, but soon after, the sheriff who was investigating was found dead. My theory - the partner escaped Stiles, killed the sheriff, then assumed the role of sheriff himself, in order to keep some track of what's going on, without having to rely on anyone else. Also, he creeped my pants off when he was insisting that Van Pelt should go with him way back in season 1.

2)I strongly believe that the given list is in fact not the precise one. Notice how Jane smiles when his Red John HQ was raided? He was certainly expecting someone to break in, hence the toothpick, but in my opinion he is throwing everyone off, giving them more names than he has picked off, while he continues pursuing his 2-3 targets with less interruptions. We know that Bob Kirkland copied the contents of the room, so when season 6 comes through I expect to find him dead, as he was unable to provide Red John with the full extent of Jane's insights, so he had to go through other people to get what he needed. Also, Lorelei's stutter while mentioning Ray Haffner's name is probably caused by the fact that she knows he is already dead.

3)
- Brett Partridge is also not RJ, he is enthusiastic about death and violence because it's in his nature, but, as they say, barking dogs seldom bite;
- Gale Bertram is a high-ranking disciple of the RJ, but not the man himself, he gets easily annoyed when he's not the smartest person in the room, and usually presents that in a way that it's hard not to notice;
- Ray Haffner is an idealist, he thinks that he can profit while being involved with Visualize, which will probably lead to his demise not long from now.
- Reede Smith is unlikely to be someone of the caliber of Red John, simply because he was incompetent enough to be interrogated on the subject of RJ by the CBI, to which as a defense he could only provide vague answers.

If luck serves me like always, none of the above will turn out right, but right now, this is my perspective of things.

After rewatching the season 4 finale I think McAllister is going to be Red John.
I think I've made some very interesting observations about the episode so let me know what you guys think

1) RJ starts the conversation by saying "Debonair at all costs". If you look at the car chase, the Lady who shoots the car with Lorelei in it comes from the Debonair intersection. She may be connected to RJ and if you look closely she makes no attempt to shoot Lorelei, only the driver and the man in the back. I think RJ planned everything out, knowing that Lorelei would get caught which would go back to "at all costs" because he didn't want to give up Lorelei  but in order to get to Patrick he had to give her away. Maybe its all part of a plan to mess with Patrick by getting her to state information that would lead Patrick to believe false ideas

2) If you look at when Patrick and Lisbon are holding hands, a random police car comes to the scene. This barely goes noticed because everyone is focusing on Patrick and Lisbon, but why would a random police officer show up to an FBI case? I think RJ is the man in the police car and it makes sense that it would be McAllister, as he is a sheriff.

My own theory is that McAllister is RJ and the rest of the suspects are his disciples. wouldn't it make sense that RJ is more than just one person? RJ can use his disciples to get all of his information. It would seem reasonable that the real RJ wouldn't want any information about himself to be known, so it's possible he's the man we know the least about which also fits McAllister.

Although my main suspect is Brett Partridge for many reasons i explained in my last theory I cant ignore the fact that Sherrif McAllister looks very suspicious to me.I dont know why, i dont have any proof about him being RJ but after Partridge Sherrif Thomas McAllister is my second suspect.About the others I am sure that RJ isnt Stiles,Kirkland,Smith or Bertram.About Haffner i dont know but he looks suspicious too especially for his age and his involvement with Visualise.

In most episodes, the identity of the killer is kept a secret until Jane set them up. And giving the identity of Red John on a list is not in their nature. I believed that the list contains some friends of Red John but not the man himself. Otherwise it would very anticlimatic because we know it would be one of the seven.

This is just an observation. There have only two other serial killers on the show. The one that RJ killed and the one in the second episode of the season 1. The sheriff appeared in the latter. It could be a coincidence. But he could be RJ or his friend.

I Just watched Red hair silver tape . Now this is not a theory just something i took into consideration . Lorelei Martins said that red John and Patric shook hands at one point . While playing rock paper scissors, Patrick and Sheriff McAllister Literally shook hands playing , LOL. cause they were shaking hands in order to play and Jane Beat him effortlessly, i just found that funny so dont be mean . . just a thought. 

"HE IS MAR"= He is Marshal? Maybe :D 

I was thinging about that message "He is Mar"

take a look at the real image ... it seems to be.

"IIe Is Mar"

we can interpret the II as roman numbers, so it could be 2E1S, or 2nd Epsiode of 1st Season. The episode where the Marshall, McAllister was introduced xD.