What is the surface made of?
Most codes require a non-combustable surface of 18 inches in front of the insert.

There are non-combustible mineral paints. Do a Google search for mineral paint or 'Keim' paint. But this would have to go over unpainted brick or stone. Like cearbhaill noted, if your hearth is made from something that can burn if a spark lands on it,(like carpet), or can ignite or pyrolize from being too close to an operating stove, (like hardwood), then you need to rip out the floor and put down something like cement board and then cover it with tiles to bring it back to even with the firebox.

Or are you talking about a fireplace which has been painted? That might be another issue all together with regard to clearance to combustibles. A little more information would help. What kind of insert are you looking at?