Line a 12 cupcake tray with cupcake liners.
Prepare and bake the cake mix accourding to intructions in the cupcake tray.
Let the cupcakes cool, and divide the frosting into four bowls.
Add a few drops of food coloring in each of the bowls and mix, to get the four colors.
Put each colored frosting in piping bags (can be substituted with a plastic bag with the tip snipped off with scissors), and pipe each color onto three of the cupcakes.
Add a peep on top of each cupcake with the corresponding color.
