Although your travel wardrobe is mostly neutral you should definitely not feel plain or too simple. The reason the Europeans appear so chic is because they add details to otherwise undistinguishable outfits.

Jewelry can add interest to your otherwise neutral wardrobe. A bold necklace will draw attention to your face and adds your distinctive personal style. Multiple or layered necklaces also achieve the same effect. Earrings can be anything from chandelier to stud it doesn’t matter.
Many great pieces of costume jewelry can be found at most department stores at a reasonable price (a steal if they are on sale). This is your chance to add color. You do not have to, nor should you, pick neutral pieces. Make sure you balance your accessories to avoid the decked out Christmas tree look. If you choose a bold necklace perhaps no earrings or go for simple stud earrings. Chandelier earrings may also need just a delicate necklace to keep from competing with the earrings. Choose a focal piece and let it shine and not compete with your other accessories.