This is what I love about Gel paste food-colorings, you can get them easily at craft stores, or online, and when used, your colours tend to be far more vibrant.
For these cuppies, the technique is simple: First, make a batch of vanilla cake. Then, divide it into the colours you wish; I made a rainbow of Red, Yellow, Green and blue.
Next, take spoonfuls of the mixes and plunk them into the cuppie tins. Layering isn't necessary; I like to have the colours beside/on-top of each other.
Layers of the colour, then it is ready to pop into the oven.
Add some icing, then some sprinkles, and they are so cute. I did add the cheerleaders as an after thought, but they were not necessary to "make" the cuppies. I just figured the girls would love them. Here's a last little shot of the cuppies all done up: