Yes, Kumpel is colloquial too.
One good way to check if a word is colloquial is to pop over to a dictionary like Leo (www.leo.org) and see if "[coll.]" is added after a word - it is usually included to warn dictionary users that the word in question might not be good to use in formal situations.
Peter--252, for British English, I would say that Kumpel is closer to "mate" than it is to "bloke" or "chap" - there is a certain "chumminess" implied to it, like this person is a friend of yours. "Pal" and "buddy" are good translations of it in US or North American English.
Komisch, in turn, is just like "funny" in English, in that it can mean either "strange" or "amusing."
Bis zum nächsten Mal,