The folks at Slate have "annotated" the finale from The Colbert Report to show who everyone is. Their video is full of code I don't want on this site so you can go to this page to watch it.
I have a feeling that Keith Olbermann, when he chose what coat he'd wear to the studio for this, asked himself, "What color jacket could I have on that guaranteed I'd stand out and be noticed?" And then when he got there and they saw it, the person who was staging everything thought, "Hey, I'll show him! I'll put him in a shot with Big Bird!"