Lactose Overdose demonstrates how to make a rainbow cake. Use either a store bought mix or use your own recipe. A white cake mix works the best. You will also need two canisters of white frosting and food coloring. Make the cake according to the directions or recipe instructions. Divide the batter equally into four mixing bowls. Add 10 drops of food coloring in your desired shades to each bowl and mix by hand. Place a large spoon into each bowl. Using half a spoonful, layer the colors on top of each other. Make sure you grease your cake pans. Use two pans of the same size to make the cake so that they will bake at the same speed. Level off the cakes. Ice the bottom layer and then add the top layer on top of it. Ice the entire cake. Slice a piece of cake to see the cool rainbow effect.