640 Loctite is green, and it sure as hell ain't "low-strength!" It's a sleeve retainer and requires more heat than red (271) Loctite for removal.
Whoops! You are correct. I looked it up and it requires heat. I do not know where I got the idea it was low strength. Anyway, Loctite states that Blue loctite can be removed with common hand tools. I only use blue on treaded fasteners.