Rainbow cake decoration with skittles and mini marshmallows. Think I'd put light blue frosting on the base of the cake, though.
Little girl's teaparty! Cupcakes baked in ketchup cups, so cute for a party or a shower! You can use a flat baking sheet too as the cups are strong enough and don't need a muffin tin. -even mini-er mini cupcakes!
Rainbow Layer Cake Recipe with Italian Meringue Buttercream. (the trick to vibrant cake layers is to use food coloring gel not liquid)