First, make the colored cake that will be hidden inside the cupcake. Follow the directions on the back of the box for the egg white recipe. This will create a whiter batter that is better for coloring.
Flour and grease the inside of an 18-inch baking sheet that has a depth of at least 1 inch.
Pour the batter into the baking sheet and bake for 20-25 minutes until cooked through, and a toothpick inserted the center comes out clean.
Allow to cool completely.
Once cool, use the 2-inch circle cookie cutter to cut small circles of the colored cake.
White Cake
Make the second white cake mix following the directions on the back of the box for the egg white recipe. The whiter the cake the better the color stands out.
Line the cupcake tin with paper baking cups and fill ¼ - ⅓ with white cake batter.
Insert a circle cake piece, centering it in the cup. Fill the cup to about ⅔ - ¾, be careful not to overfill.
Bake for an additional 18-20 minutes, or until cooked through. Allow cupcakes to cool completely.
Buttercream Frosting
Scoop the frosting out of the tub and into a mixing bowl.
Use a hand mixer to whip the butter to give it a lighter and fluffier texture.
Optional: Add a tablespoon or two of heavy whipping cream for a more homemade flavor. This will thin the frosting, so if needed add some powdered sugar to thicken the frosting back up. It needs to be thicker to use in a pipe bag.
Divide the frosting into three different mixing bowl. Create a bowl of pink frosting, a bowl of blue frosting, and keep one bowl white.
Layout a large sheet of plastic wrap and add rows of the different colors of frosting. Roll the plastic wrap so you know have a tube of multi colored frosting.
Insert the tip into the pipe bag and then add the tube of frosting, leaving it in the plastic wrap. Don't worry, it will squeeze out of the plastic.
Pipe swirls of pink and blue frosting onto the top of the cooled cupcakes.