I just saw a photo of the Duchess of Cambridge in the Royal Watcher tumblr, in the photo (below) it seems that she is wearing sapphire earrings but I don't recall seeing those before. They look a lot like the emerald earrings she wore on the three-day trip to New York.
Could it be that the same earrings with interchangeable emerald and sapphire? Or is it just a photoshoped version?
Emerald version worn on the occasion of the St. Andrews 600th Anniversary Dinner at the Met (Dec. 9, 2014)
Sapphire version (http://royalwatcher.tumblr.com/post/110918276922/54-100-photosets-of-the-duchess-of-cambridge)