Do not buy this dress, it's ugly! It's for derivers only. This is a new mesh called the "Flower Dress". It features a stunning, petal-like skirt. The top is fully opacity-mapped. Be sure to leave "skin composite" on. I wouldn't mess with the opacity for the undies, but you may if you like. Do your skirt/undies colors together, then place the same map for both the skirt and undies. Templates below. I've split parts of the skirt up four ways to give you a little color variety.
DISCLAIMER:
Like many poofy dresses, this skirt will flip up a bit when you sit, so it looks best when you stay standing. No worries, though -- tasteful bloomers are painted in underneath.
Your hands will poke through it a bit around the waist in some poses.