Preheat the oven to 350 degrees Fahrenheit. Spray three 8-inch cake pans with cooking spray and set aside.
In a large mixing bowl, using an electric mixer or stand mixer, combine the 2 boxes of cake mix, egg whites, oil and water until smooth.
Evenly divide your batter between 3 bowls. Use the red food dye in one, blue food dye in the other and leave one white. Add few drops of each to get your desired shade. Mix each until combined.
Pour red batter in one pan, blue in another and white batter into a third pan.
Bake in preheated oven to 350 degrees Fahrenheit 20-25 minutes or until a toothpick inserted in the middle of each cake comes out clean.
Let the cakes cool in their pans for 5 minutes before inverting them onto a cooling rack to finish cooling completely, about an hour.
In a large mixing bowl, using an electric mixer or stand mixer, combine the softened butter with the powdered sugar and whip until light and fluffy.
Place the red cake on your cake plate and spoon a bit of the frosting in the middle and spread out evenly over the top of cake.
Stack the white cake on top of the red, add frosting to the top of the white layer and spread out evenly then repeat with the blue cake.
Once your layers are stacked, finish completely frosting the cake with the buttercream.
Add sprinkles and maraschino cherries to decorate, if desired.
Place the cake into the fridge for at least an hour to chill and set up.