Oh yes, I will second that as well. Using some spray paint removing chemical will likely take the blue off right with it. I would personally NEVER put $4 worth of spray paint on a few hundred dollar (or even thousand dollar) investment, but to each his own.
If you want the spray paint off, I'd very seriously consider getting it re-coated in Duracoat, KG Gun Coat, Cerakote, Ion Bond...SOMETHING that will actually protect your gun, not just muck it up. You really have no idea what the condition is under there, It COULD be fine, It COULD be very bad.