I've been using nail polish to paint jewelry for a few years, mainly because I always have it around and never feel like going to buy paint. There have been some great DIY posts re-doing jewelry with nail polish, its such a quick and easy way for a new look.
I got these House of Harlow inspired necklaces off ebay awhile ago. I liked them, but I wanted a different color. Five minutes and little nail polish later, I have a brand new necklace! The best part is, BOTH sides are available for color repaint, so it's like having four necklaces! I'm thinking of doing one in a coral, or bright neon color next!