Mix the white cake mix following the directions for the egg white instructions.
Line a cupcake pan with the 12 white cupcake liners.
Fill each cupcake liner ¾ full with the uncolored white cake batter.
Bake the cupcakes for 12 minutes, turn the pan and bake for another 8 minutes.
While the white cupcakes are baking add about 12 drops of the red gel food coloring to the remaining cake batter. Mix for 1 minute.
Put the red cupcake liners into a cupcake pan and fill ¾ of the way full with the red cake batter.
Bake as directed. Cool both batches of cupcakes completely before frosting.
Cupcakes may be made the day before decorating and serving.
For each batch of the frosting
Start with the uncolored white frosting first. In a bowl beat the softened butter until light and fluffy, about 2 minutes.
Add 1 cup of confectioners sugar and mix on low until combined with the butter.
Add the remaining 1 ½ cups of sugar, the vanilla extract and milk or cream to the bowl.
Turn the mixer on low and slowly beat the sugar until combined.
Turn the mixer on high and beat for 3 minutes until light and fluffy.
Remove the white buttercream frosting to a small bowl with a lid. Place the lid on and set aside.
Add the next stick of butter to the mixer (no need to wash the bowl at this point).
Repeat the previous instructions.
Once the frosting is done add about 12 drops of blue gel food coloring.
Beat until the food coloring is mixed in well.
Remove the blue frosting from the mixing bowl and place in a smaller bowl with a tight fitting lid.
Wash and dry the mixer bowl well before the next batch of frosting.
Repeat the previous instructions for making the buttercream frosting only, this time, add about 12 drops of yellow gel food coloring to the finished frosting.
Mix well and place in a small bowl with a tight fitting lid.
To Decorate Captain America Cupcakes
Place the large star tip into one of 12-inch decorator bags. Fill the bag with the blue frosting.
In a second bag place the other star tip. Fill this bag with the white frosting.
Swirl the blue frosting over the top of each of the white cupcakes, (being sure to reserve about ½ cup of the blue frosting for the Iron Man Cupcakes).
Place a white star using the uncolored frosting in the center of each of the blue frosting on each cupcake.
Place 8 red original Skittles around the edge of each cupcake.
Stick a Captain America Cupcake pick in each cupcake if using.
Store frosted cupcakes in the refrigerator until ready to serve.
To Decorate Iron Man Cupcakes
Wash the closed star tip. Place the star tip in a clean decorator bag. Fill with yellow frosting.
Place the small circle tip into a clean decorator bag. Fill this bag with the reserved blue frosting.
Swirl each red cupcake with the yellow frosting.
Add a blue circle to the center of the yellow frosting on each cupcake with the blue frosting fitted with a small circle tip.
Stick an Iron Man cupcake topper in each cupcake if using.
Store frosted cupcakes in the refrigerator until serving.