Why does oxidized copper become green? Why does oxidized copper turn green? I am sorry if this question is too basic, but am really stumped here. It would be helpful if one could provide a research paper or website with your answer.
Copper oxide is not green, but green verdigris, basic copper carbonate (or acetate) forms on copper exposed to air and moisture.

Heating copper in air can form a near-transparent film of copper oxide, which can exhibit all the colors of the spectrum due to interference of light. The same effect cause a "rainbow" in oil slicks on water.