This Rainbow Unicorn Cake is ready for birthday fun! Complete with a colorful pastel mane and a gold fondant horn, this unicorn cake is great for birthday princesses of all ages. A great project for beginning decorators, this cake uses the pony pan to make this shaped cake. Though we used fun pastel colors here, you can make the mane whatever color combination you'd like! Try bright and bold colors or use a variety of hues in the same color family for a completely different look.