This may be a really stupid question but can you use the icing colors to make the layers in a rainbow cake or should I use regular food coloring?

I used icing colors when I made my rainbow cupcakes. Use sparingly at first, then add until you get the desired color.

Thanks! I am thinking this will be a really neat cake to make for my twins preschool class. I'm still trying to come up with a way to decorate it though. I am going to use a rectangle pan so I hope it works since everything I find uses a circle pan.

The kids will enjoy them! Are you going to layer the colored batter?

I think I'm going to layer them in the pan before I bake it. I like the swirled look compared to staight layers. I am just hoping it works with a rectangle.