In the general scenario of chemistry, copper is a metal that is highly resistant to the chemical reactions emitted by the atmosphere and sea water. It was the first metal ever used by man. About five thousand years ago, when copper reserves were discovered by man, they found a number of uses for copper that included making tools, ornaments and weapons. Nevertheless if copper is exposed to any of these two elements, it has a strong tendency of changing its color to green. The color acquired by the metal is actually the result of the formation of a thin coating of green basic copper carbonate, which is generally referred to as patina or verdigris. The latter name is derived from a word of old French vert de Grece (green of Greece). This beautiful shade of green is often observed as a veneer on copper roofs or statues, specially if there is a close proximity to the sea.
Because it feels like turning green!