I just want to point something out here.  A lot of people are focusing on what Red John looked like or walked like or talked like, or how he holds his tea cup or how his hands look.  This from the episodes where we just catch glimpses of him in disguise or from the back or just his hands.  But I assure you, whoever they used to portray Red John in these scenes is NOT the actor who plays the actual character of Red John.  They just use some guy on the set to fill in the space.  It would be WAY too expensive to get the real actor to do these scenes, not to mention the security issue of allowing everyone on the set to know who Red John is.  So seriously, forget about all of these physical characteristics.  Focus on what kind of person Red John has to be.