If your white gold doesn't come with rhodium plating and you want to improve its aesthetic appeal, we recommend you plate it at your local jewelry store.
Another thing you can do is polishing your aquamarine earrings or any other type of aquamarine jewelry at your jeweler's store.
On the chance that you bought a piece that has rhodium plating already, then you'll need to re-plate it every 2-3 years. Otherwise, the metal loses that extra shine.