Patio Furniture Glass needs to be replaced or cleaned?

I just bought some patio furniture with a glass table top from a garage sale. On the underside of the glass is some kind of solid color, but I can't figure out what it is, and therefore, figuring out how to remove it. I tried everything I could to remove paint from glass (paint stripper, razor), with no luck, telling me that it must not be paint. Any ideas as to what it is? The edges of this 'color' have been chipped away from the edges of the glass, but I can't seem to scrape anymore off. I really don't want to have to buy new glass because it seems expensive. Any recommendations?