Prepare buttercream icing, divide and tint portions blue and yellow, reserve white. Assemble cake layers on foil-wrapped cake board, spreading thin layer of buttercream icing between layers. Spatula ice cake smooth. Using tip 3 and white icing, pipe swirls on cake sides. Using tip 18 and blue icing, pipe stars on cake sides. Using tip 6 and yellow icing, pipe top and bottom bead borders. Position cookie on cake top, securing with a swirl of buttercream icing.
*Combine Lemon Yellow and Golden Yellow Icing Colors for yellow shown