This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Both metal and copper oxidize when exposed to oxygen and this is a natural process. Copper that is exposed to the outside environment is more likely to turn green and that is why copper vases and decorative pieces in gardens are often green.
To be fair, blue and green flames can be due to copper. Flares, fireworks, and decorative fireplace logs use copper to create green colors. And stray copper can cause green and blue flames in other settings, for example, wood with copper-based fungicides or paper with copper in the ink or copper staples.