Ingredients
1
box yellow cake mix with pudding
Water, oil and eggs called for on cake mix box
1 1/2
cups butter, softened
5
cups powdered sugar
2
teaspoons vanilla
2
to 4 tablespoons milk
Blue, purple, green and orange gel food color
Preparation
Heat oven to 350°F (325°F for dark or nonstick pans). Grease bottom only of 1 (13x9-inch) pan. Make cake mix as directed on box using water, oil and eggs.
Bake 28 to 32 minutes or until a toothpick inserted in center comes out clean. Cool 10 minutes in pan; remove from pan to cooling rack. Cook completely, about 1 hour.
Meanwhile, beat butter with an electric mixer on low speed until creamy. Beat in the powdered sugar, 1 cup at a time, until smooth. Add vanilla and milk, 2 tablespoons at a time until well combined. If frosting is too thick, beat in more milk.
Use 1/2 cup frosting to frost a thin layer over entire cake. Divide remaining frosting into four bowls (about 3/4 cup frosting in each bowl). Mix blue, purple, green and orange food color, one into each bowl, until desired hue is reached.
Place each color in individual resealable food-storage plastic bag. Cut 1/2 inch off one corner of each bag. Pipe a dot of blue frosting and use back of teaspoon to pull frosting slightly. Repeat with remaining colors, alternating colors as you cover cake, slightly overlapping dots of frosting.
