Prepare cake according to package directions.
Separate evenly into 3 bowls. Using the food coloring, tint each bowl differently.
Bake according to package directions; allow to cool.
Remove from pans and slice tops off cakes so they are all level.
Place bottom layer onto cake plate. Frost top with frosting. Repeat with each layer.
NOTE: Use your creativity in coloring the layers. Either tint one bowl lighter and each one getting darker after that, or each bowl a different color.