I guess it would depend on if it was water based or epoxy paint. Check with a reputable paint store for removing solutions.Any type of scouring will scratch the tile surface or dull it. The grout may be another story as the paint probably soaked into the grout as opposed to laying on top of the ceramic tile. You might be able to apply a grout colrant over it after the tiles have been cleaned. Something like www.groutdye.com