Why not bring a smile to the face of someone eating a cupcake today (not that cupcakes on their own don't bring a smile!). It's a fun surprise when you bite in to see all those pretty colors.
They are also perfect if you are hosting an art party, rainbow party, 60s party (they look kind of tie dye on the outside) or anything else you can think of. I made mine as a way to make the last day of preschool for my daughter a little brighter (she's leaving her classmates behind to go to summer camp in our lake community and she's sad).
There are many how-to instructions on the web. The number of colors and the hue of the colors are up to you. Here's one I used (Family Fun is a great magazine and fantastic website...always doing projects from them): http://familyfun.go.com/recipes/taste-a-rainbow-cupcakes-842128/
And now the best part, a photo of the yummy cupcakes as I made them!