One of the main concern of my customers, especially those who are not used to wear base metal jewellery, is this: I’m afraid my fingers or lobe will turn green. And yes it will happen, that’s a normal chemical reaction due to the pH of the skin interacting with the copper present in the metal alloy (even silver and gold contain copper, so in theory the could turn your skin green too, just in there the amount of copper is much lower).
There are two main solutions for this problem, though none of these is final:
1) the first is plating your piece (gold, silver, rhodium etc). This is done by a professional and I will dedicate a post about plating alone, is a complex and interesting process;
2) the second solution is the creative one (always my favourites!) and it’s about to apply a layer of transparent nail polish inside the shank of the ring, wait until it dried and then apply another one. If you prefer, there is a specific thing for this purpose and it’s called “Allergy Jewelry Sheld” (you can find it here -link not affiliated-)..
Please keep in mind that both these solutions (plating and the nail polisher/Jewelry Sheld) are temporary: with time, by wearing your pieces the plating/coat will wear off.