My niece is getting married and has requested a rainbow flavored/colored wedding cake (she apparently had a piece of one before at a party and loved it!). Each tier would have a layer of strawberry, orange, lemon, lime and grape cake with a thin layer of white buttercream frosting in between each layer. The outside of the cake would be all white of course. I can use food coloring but I can't figure out how to get the flavorings. (I would want to keep all of the layered textures the same.) Any suggestions?

If you're using mixes, one possiblity would be to sub in fruit juices for the water used in the batter, and then maybe some food color to make the colors vibrant. I'd suggest doing some experimenting. Here is a link to one on Martha Stewart's site http://www.marthastewart.com/recipe/rainbow-cake