What turns granite or marble blue?

Yes, indeed it is chemical. The presence of Iron and titanium impurities in just the right amount and right crystal structure can cause the blue colour. read more

A gray-blue slab of marble might have darker blue veins; a gray-pink slab might contain veins that are quite rosy-red in color. Exotic Gold Veigned Granite Countertop Beauty is subjective, of course. read more

If the granite is turning green on the top or by the seams, it is"blooming" caused by a chemical reaction. It's been covered on how to treat. However, what the op seems to be talking about, green on the edge, is from copper in the stone oxidizing. read more