What we know about The Doctor (spoilers)

I would argue he played a Doctor that was more alien, non necessarily likable, and was only truly unstable for his first story (Twin Dilemma) or when the story was running short and needing padding (Time Lash). The idea was that he would calm and mature over the first season, so the unstable would trim away and be gone by the time they reached the Dalek story. But Time lash was running about 5 minutes short one episode, so they wrote in a filler bit with The Doctor being nuts and annoying Peri.

Six-ee was more dangerous because Colin Baker liked doing the action sequences. One of the misunderstood scenes from "Vengeance on Varos" is when wrestling with the technician using the sheet of whatever between them, The Doctor was trying to keep the man from falling into the acid, but the tech overbalanced and the Doctor had to let go to avoid falling in. Doesn't quite read that way unless you are looking for it.
Again, he was just starting to get to play the Doctor the way he wanted right at the end. Take another look at Trial of a Timelord (specifically the last half), and you can see what would have been if he'd been allowed to continue.

Big Finish Productions got hold of the scripts and drafts for the year that was supposed to happen afterward, and got the rights to produce the stories as "The Lost Years" or something like that. Seems working on them brought back a whole bunch of memories for Colin Baker.
Again, if you haven't tried BFP, I strongly suggest investigating them.

Nagol said:

I have no doubt Colin Baker could have been a much better Doctor.

But he played a Doctor that was

more dangerous, more urgent Doctor
older, fiercer, madder, less reliable Doctor
going to go quite different with the Doctor.
he is mad and dangerous and difficult.”

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I went back and checked out some of the Colin Baker episodes, and I think he was actually quite good. But i do think it would probably be a bit much for fans if they were to repeat that extreme end of behavior in the show now. I think they are going more for Tom Baker or Eccleston here, judging by the full quote:

Steven Moffat: “Our vague idea is… the last two Doctors have been brilliant, and have been your ‘good boyfriend’ Doctors. But the Doctor isn’t always like that. There is the sort of Tom Baker, Christopher Eccelston end of the spectrum, where he is mad and dangerous and difficult.”

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