Corsets and brides go so very well together. For brides, corsets can serve as a foundation to their dress (aiding in the fit and accentuating the silhouette), be an exposed element in their ensemble, or have a special place in their trousseau and possible boudoir photos. Even the most budget minded individuals often consider their wedding the perfect time to splurge a little and invest in a high-quality corset that, unlike the cake, flowers, and gown itself, will last and continue to be wearable long after the ceremony itself has concluded.
Foundation corsets can be tricky --- remember that a corset is not a magic fix that will make a dress two sizes too small suddenly fit. If you just need your waist nipped in a little bit, maybe some strapless bust support, then absolutely, a corset is the way to go. If the ribs and/or bust of your dress are too small, however, a corset is more likely to add bulk (because of the layers of fabric and steel) than reduce it. Talk to your corsetiere about options for sleeking down construction, such as mesh or other single-layer construction, and internal bone channels, but if the zipper won't slide without the corset, it's time to consider alterations or a different gown. Low-back gowns, full busts, and corsets are also a tricky combination; it might work out while the dress is on, but if the back is lower than bra band level, it's nigh upon impossible for the front of the corset to offer adequate support on its own, particularly since the back will need to be on the loose side to avoid creating a muffin effect.
Regarding the color of a foundation corset, something close to your skin tone will pretty much always be the most unobtrusive, but if you don't want to be stuck with a brown or beige corset after the wedding, you can actually get away with a darker or bolder color if your gown has several layers of lining and/or if you make sure to match the rest of your undergarments to your corset to avoid a striped effect. Be sure to test this theory out in a variety of lights and in photos to avoid any surprises on the big day or when you get your pictures back.
Now, if you want to show off your corset (and resulting hourglass figure) a little bit more, you might want to consider having it incorporated into your ensemble. Generally this will mean the skirt is a separate piece from the corset. Most expert corsetieres also have the skills to create other garments and so you could have both pieces custom-designed together together with accessories such as a bolero, custom garter, or your veil. Surprisingly, the cost for one-of-a-kind, custom-fit wedding ensembles from a corsetmaker is not so different from what you'd pay for a factory-made, off-the-rack dress from a pricier bridal store: roughly in the $5-$10k range. Sparklewren (Birmingham, UK) and Dark Garden (San Francisco, CA) are particularly experienced with bridal couture.
For a classic bridal boudoir look, most high-end corsetieres creating handmade pieces should be able to accommodate both your wedding and personal aesthetic, but I'm particularly fond of Glasgow-based Crikey Aphrodite's delicate white-on-white lace and sheer corsetry. If you're planning to wear your corset on your honeymoon, make sure you have an exit strategy! I do not recommend closed front styles for bedroom corsets. This is a perfect opportunity, however, to train your partner in proper lacing and unlacing techniques, if treated as an intimate moment rather than a necessary inconvenience.
When I do consultations with brides, I frequently hear that the bride is being slightly bullied into wearing a white dress (at the behest of her mother, mother in law, or even fiancee). I'd like to take this moment to remind you that, not only is it possible for your foundation corset's color to match your taste and personality, but the "tradition" of white weddings is pretty new-fangled. Depending on the time and place, even black could have been an appropriate color for a wedding gown. So if you're showing off a corseted ensemble, wave that fact around and order it in whatever color(s) you like!
Lastly, I know a lot of brides either a)intend to lose weight before the wedding, or b)don't intend to, but have it happen anyway. If you're ordering a custom corset, don't order it too far in advance. Your measurements may or may not change. Ask your corsetiere what turnaround they would recommend; generally 2-6 months for custom, 1-3 months for ready-to-wear. You can do a consultation and lay down a deposit with the corsetiere as early as their queue allows, you just don't necessarily want any sizing to happen until a little closer to your date. Make sure you'll also have time to get your gown or skirt tailored to fit both your body and the corset. Regardless of your size, a good fit is key to the look, support, and comfort of a corset.