A. This problem may require the services of a professional stone restoration contractor. First, try mixing some odorless ammonia and water with a 50/50 mix ratio. Wet the tile and apply the solution with a soft scrub brush. Agitate it and then rinse with clean water. If this does not work, it will need to be cleaned with acetone or a mild acid, however, we do not recommend trying this yourself. Acetone can cause health problems. Acid may give you the desired results, but since marble is an acid-sensitive stone, chances are the acid will cause acid etch damage to the finish. A professional stone restoration contractor may be able to remove it without causing etch damage or restore the honed finish if etch damage occurs.  If the grout bled into the stone, a professional stone restoration contractor may be able to remove the grout and poultice the stain from the stone, but this would be a labor-intensive effort. You may be better off replacing the installation in this case, but be sure to let a professional stone restoration contractor have an in-person consultation to confirm such drastic measures are necessary. If you do not have a PRO, contact us.