It's no secret that a natural-looking hint of warmth can do wonders to boost your appearance, especially under bright flashbulbs. Since real tanning isn't a bright idea, start considering faux tan options such as Almay Self Tanning Gel ($8), which is tinted so you can see where you're applying it. (You can find more products and ideas here.)
Here's a tip to help protect your gown: Test out any new tanning method by wearing a white shirt the day after application, and see if any rubs off on the inside by the end of the day. If the shirt is clean, your dress will be safe.