Well, the show has a massive cast, but the primary characters are probably the first three, since those are the guys that the reporter, Evan Wright, was riding along with. They also have a gunner, but he's up on top all the time and not involved in the conversations inside the vehicle. The last two I just included because they were interesting to me. Actually, the lieutenant probably gets nearly as much air time as the main guys, and there's dozens of other characters that get significant air time every episode.

Generally, the reporter doesn't even involve himself in the story that much, though. It'd actually be very interesting to know his type because you have to figure the whole thing is viewed through his lense, as he wrote the book and also is one of the writers for the show.

Here's a video of the real Colbert, the real Wright, and some clips from the show:



They show some footage that hasn't aired yet in there and Trombley came off as quite different. As for Wright's type, I still have no idea.

I definitely suggest you check the show out, it's fantastic.