Ive noticed the same on a couple of ads for Analysis Plus Oval 9. I didn't purchase for that reason. For as much as I (we) obsess over the slightest things in our systems seeing a green copper wire just wouldn't work for me.
Corrosion
On a Shunyata Diamondback power cable I use, which has clear insulation, there is green oxidation visible on parts of the shield. Can that have an audible effect, is it a concern?