Follow the directions on the cake mix and prepare the batter. Divide the batter into three bowls, coloring one red, one green and leaving one white. Following the instructions on the color right systems makes perfect colors every time.
Layer the cupcakes with 1 tablespoon of batter of each color. Do not over fill. I was trying to obtain a more layered look, but they had a mind of their own.
Bake 24 cupcakes according to the instruction and cool completely.
Prepare your frosting. Mix the butter and shortening in a stand mixer and mix for 5 minutes to combine. Gradually add in the sugar, vanilla, and milk. If you want to keep your frosting as white as possible, use more shortening and less butter and use clear vanilla.
Prepare three piping bags with one coupler.
Add about ¼ - ⅓ cup of frosting to a piping bag. You'll have three bags of frosting. Carefully add all three bags to one master bag with a 1M tip. Secure the coupler and decorate.
Add any sprinkles and decorations you want to make them pretty.