A. I applaud your desire to add some personal style to a basic navy suit. Adding a belt, colorful or not, adds a chic touch to a fitted jacket. Try also wearing a colorful or printed underpinning and a bright handbag. Depending on how conservative your office is, you can add patterned tights or a colorful shoe. Jewelry, like this season's statement necklace, or a scarf can also add interest.
2. colorful jewelry and underpinning will brighten up a dark suit (look shown here is from jcrew.com)
3. a colored shoe with dark tights (or a bright opaque tight with dark shoes)