Preheat the oven according to the directions on the cake box and spray two 9x13 pans with cooking spray.
Make the batter according to the box directions.
Divide the batter in half and add red food coloring to one of the halves.
Mix the batter with the food coloring until you get the desired color.
Pour the divided batter into separate baking pans and bake each for 15 minutes.
Allow both to cool.
Cut 12 circles from each color cake using a 2"-2 1/4" cutter (or wash an empty tomato paste can).
Place alternating red and white cake circles in jar until 4 slices are in place.
To make the icing, cream the butter in a medium bowl
Slowly add in the powdered sugar and milk as needed, until everything is incorporated and frosting is the right consistency.
Add several drops of blue food color and whip a few more minutes to get an even color.
Transfer the frosting to the corner of a zippered bag and clip a small piece off the corner to pipe.
Frost cakes.
Melt white chocolate by heating in microwave and stirring and repeating until melted and smooth.
Pour melted chocolate out onto a sheet of wax paper as evenly as you can and allow to set until nearly solid.
Cut stars out with a small star cookie cutter and place on top of frosting.