How do you get green off neck from necklaces?

It is certain types of metals that react with your skin to cause the green discoloration. Gold or white gold will not discolor, but they are expensive. For the costume necklaces you get at places like Claire's or Icing, you can do a few things. You can paint it with a thin coating of clear nail polish. Wear the necklace for short periods of time. Take it off when you go to bed, and don't wear it swimming or in the shower.