My neice was telling me that she was going to make a "rainbow birthday cake" for one of her good friends. I never heard of this type of cake and I asked her if she would send me pictures of it when she was finished with it. She sent these beautiful colored photos.
She said she basically made a white cake mix, divided it into however many different colors that she wanted to, and mixed in the food coloring paste. Once they were all mixed, she poured each color in the middle of the pan, flattening the batter each time. She included a link that gives good directions on exactly how to make it, if you are interested. The link is; http://www.playinghouseblog.com/2009/07/rainbow-cake.html
My neice's creativity and sense of adventure has helped her create many delicious and pretty deserts. I am sure her friend was thrilled to receive a homemade gift like this one.