TPF may earn a commission from merchant affiliate
links, including eBay, Amazon, and others
Generally speaking, Tiffany has excellent customer service, so I would guess that they would take it back. They once sent me a $100 gift card just because a necklace I ordered arrived 1 day later than expected.
I had this happen to one of my rings from Tiffany. They said that they put some special coating on their sterling silver and that my skin was probably reacting badly with the coating. They offered to buff the ring and take that coating off for me. I got it back and have had it for over 3 years with no other problems. I would suggest trying that before you return it! If they do buff it out and it still turns your finger green then I'm sure they would let you return it!