Swank Underpinnings carries poufy half slips in all lengths to accentuate that 50's silhouette. As a designer of primarily 50s dresses my advice to you would be make sure your under slip is worn separately from your dress (read: yes, as in a whole separate piece). Why? You don't want to add bulk to the waistline. Wedding gowns have enough heavy duty handiwork going on inside, why add more? I know most gowns come with built-ins, but do ask your salon when placing the order to have the designer send your slip as a separate component from the gown.
Adding color underneath your dress hints at it once you lift your skirt. Or better yet, how about going for the Peek-A-Boo factor? That means that a little touch of red or purple or whatever color you want slips beyond the hemline. How that for chic . . .?