In a large mixing bowl, using a hand or stand mixer, cream the butter for 2 minutes, until light and fluffy. Mix in the vanilla extract and lemonade flavoring (start with 1-2 drops as this flavoring is strong!).
Slowly mix in the powdered sugar, 1 cup at a time, while alternating 1 tablespoon of the half. Continue to mix until creamy and stiff peaks form.
Divide the frosting into 3 bowls. Add the blue food coloring to one bowl and the red to the other, 1 drop at a time and mix until desired color is achieved. Leave the other bowl without color.
Insert the larger piping bag into the large glass/mason jar. Using a frosting spreader, add a stripe of the red on one side and then another across from it. Repeat with the blue frosting. Carefully fill the bag with the white frosting.
Before frosting your cupcakes, squeeze out a bit onto a plate until you see all the colors come out. Frost your cupcakes and garnish with the sprinkles desired and enjoy!