Some time ago when I was active in BPCR I noticed that pulled bullets had green in the lube grooves. Moreover, some felt glued in and came out hard with a loud crack. The lube bands were green. I conducted an experiment by coating several pieces of brass with various lubes and leaving them for about a month. Most turned green, but the amount varied. Unfortunately I didn't keep permanent notes. IIRC, the worst was a lube by a guy, since deceased, out of California. Sagebrush produced a lot of green. NASA lube was pretty good. Common lubes such as SPG were in the middle. Again, apologies for my sketchy memory. Discussions of this phenomenon seemed to point to animal fat like lanolin as the main culprit. Probably an interaction with the brass. When I was shooting actively, I tried to use fresh loads for competition. I also went to paper patching, which avoids the problem altogether. I had some good photos, but they were in Photobucket, so held for ransom which I won't pay.
Just sharing my experience, FWIW.
Paul
