Onyx, I've made loads of zebra and rainbow cakes and you can use any type of cake you want, but they have to be the same consistency otherwise when you pour them into the pan, they wont spread properly and the layers/stripes wont look right. The way I do the rainbow zebra cakes is to make a couble quantity of batter, then split it evenly into however many colours I want to have - usually 6. Then I add the colouring to it and then alternatively pour it into the pan. Have you seen the FB pics I have of when I've done them? If you do cupcakes, you will literally only need a teaspoon of mix for each layer if you want a few layers/stripes, otherwise you can have less layers/stripes by using bigger spoonfuls of batter.