Preheat oven to 350 degrees and then spray or line a standard muffin tin.
Add cake mix to a large mixing bowl. Using a hand or stand mixer, mix in your ingredients and blend well.
Evenly separate the batter into 6 containers and color each with the 6 food colors until desired color of each is achieved.
Add a small spoonful of each color of the batter into the muffin tin until each is about 2/3 full.
Bake for 18-20 minutes, or until a toothpick comes out clean. Allow to cool completely before frosting.
In a large mixing bowl, cream the butter and beat until light and fluffy, then add in the vanilla extract. Slowly mix in the powdered sugar, while adding a bit of the half and half or milk. Continue to mix until creamy, and lastly add in your marshmallow flavoring.
Prepare piping bag and fill bag with frosting. Frost cupcakes and top each cupcake with the rainbow sprinkles.
Serve and enjoy.