Thank you all for any advice you can give me in advance.  I appreciate your knowledge.  I looked at about 2500 sf of honed limestone today and it really is getting badly stained.  The owner says the stains in the attached photo are from coffee.  I realize that they would probably come out with a thorough honing process, but my question is Will they just return when coffee is spilled again?  I use a penetrating sealer, no topicals, and I am afraid that the sealer won't help this problem.  What would you suggest I do to this floor that the owner wants to keep honed?