it doesn't turn blue or turquoise.......turns it green. why? There are several 'green' copper salts which are combinations of the metal copper and various other chemicals. Examples include copper sulfate and copper acetate. You will note that the green color of the Statue of Liberty is the result of the exposure of copper to the environment which causes oxidation and the production of green salts. As far as your skin, we constantly release chemicals from our bodies in the form of sweat. These materials are generally acidic in nature and will cause metals to 'corrode', or turn, at least on the surface of the metal, to a salt compound of the metal. Exactly which of the 'salts' is forming I cannot say. But the green on your skin near the copper is the direct result.