Coating your Baphomets with nail polish was a wise decision. In the future, you may wish to consider using Krylon clear enamel (available at most hardware stores in a spray paint style can) or Renaissance Wax. I use both on a regular basis, and can explain the application process if you wish. However, any protective coating will wear off over time, which is why your silver is changing color.
Sterling silver is a fine silver/copper alloy. The the oxidation of the copper explains the green-oxidizing (think of old copper roofs). Oxidation is only occurs at the surface level and is completely removable. The ideal solution would be for you to have a jeweler do a clean & polish. They should use various grits of sandpaper, a lapidary wheel, and several grades of buffing abrasives to remove all signs of wear and restore it to like new condition. It is important that the jeweler you go to has experience with silver, gold is much easier to clean and maintain. You could also request that they raise the fine silver (a.k.a. depletion guild when referring to gold), which would remove the copper from the surface of the Baphomets so that there is a layer of fine silver on top (which oxidizes much slower than sterling).
I don't have enough information to tell you exactly what to do, but I will make a few suggestions that will hopefully be helpful. If the green is simply on the surface, you should be able to remove it using a brief dip in a commercially available silver cleaner followed by hand-buffing with a red rouge polishing cloth (I use the Sunshine brand). If the greenish color is in the recessed areas AND your Baphomets have a satin/brushed/matte finish, you can use toothpaste and a soft-bristled toothbrush, followed with the rouge cloth. If your Baphomets have a mirror finish/high polish using any abrasive (including toothpaste) will ruin the finish (chances are this isn't an issue, if they've been worn enough that the nail polish has come off a high polish will have vanished a long time ago). Oxidation occurs more slowly on pieces that have a high polish because there is no "tooth" for the oxidation to hold on to.
I think about and work with jewelry for the vast majority of my day, even my free time. Bring up jewelry or metalworking and I'll be talking for hours. If you have any other questions, I'm around.
P.S. Thanks for the page Scion
... but do you really think I'd gloss over a post with the word jewelry in the title?