It is a landscaping stone and I'd like the design to be tinted darker green. I would like to put something in the polyurethane to stain it so I won't have to paint it. I want stain, not paint. Is that possible? WalMart, Orschelien's and local lumber store won't touch it or answer our questions, we have to go 35 miles in either direction to find a "custom paint store".