User blog comment:General MGD 109/Pheonix, Monster or not?/@comment-5014819-20120410221228/@comment-3481504-20120410234238

About vessels:

Well, of course The Colt wouldn't work on a demon's true form, as it's incorporeal, and for the most part practically intangible. Making them only eligible to death when possessing a human, besides forces like God, Death, Archangels and Angels, characters who likely could kill them regardless.

It simply affected Eve's vessel because of Eve's high vulnerability to it, like I said, no, like Dean said, it can hurt humans.