How do frost dragons breathe frost?

Dragons breathe anything using the magic flowing throught the things around them. They're like magicians (The real ones, not the crappy Vegas ones) except they usually channel it through they're mouth, and in the terms of dragons, that would be fire, ice, lightning, acid, poison gas, pure magical energy, and a gaseous substance that transmutes anything to diamonds. The can also heal, but that is rarelly used.