Wouldn't this make and unusual and amazing wedding cake?
Imagine a gorgeous all white tiered cake covered in fondant. With detailed piping and maybe even some white sanding sugar to make it sparkle. And once cut the amazing bright colorful center is exposed! I think it would make for amazing photos and cause everyone to be surprised.
You wouldn't have to go all out for the Rainbow theme. Doing just a few of the wedding colors would also be great.
All photos and cake tutorial from the fabulous Hostess with the Mostess