Originally Posted by
cyccommute
The fork I have has metal inserts that the brake bosses thread into. I relatively certain that is the case for carbon forks with cantilever bosses.
That makes sense. In which case blue loctite makes most sense, as it creates a reversible bond (i.e. you can, eventually, remove the bosses if you really need/want to).
EDIT: don't use red loctite, as that requires high temperatures for removal, something a composite material would not survive.