Prepare white cake mix according to the manufacturer's instructions. Deposit 10.5 oz. batter each into 2, 6-inch rounds that have been treated with pan spray. Deposit 1 lb. batter each into 2, 8-inch rounds that have been treated with pan spray. Deposit 2 lb. batter each into 2, 10-inch rounds that have been treated with pan spray. Bake at 350 ºF until cake springs back lightly when touched. Let cool completely.
Build a 3 tier cake made up of 2-layer cakes in 10”, 8” and 6” diameters filled and iced with whipped topping making sure to use internal supports. Separate equal parts white flat icing into 5 bowls. Add red, orange, yellow, green and blue gel food colorings, 1 to each bowl until desired color is reached. Pipe warm icings in alternating colors around the edge of each cake tier, allowing icing to drip down the sides of the cake.
White Cake, VelveTop, Non-Dairy, Flat Icing, Red, Orange, Yellow, Green, Blue, Layer Cake, Party, Tiered