Prepare decorating bag with coupler and light pink icing. Using tip 12, starting about 2 in. from edge of first sponge layer, fill in centre of cake; smooth with palette knife. Prepare three decorating bags with couplers. Fill each bag with ½ cup of one color. Prepare five additional decorating bags with tips 1M, 2A and 4B. Fill each with ½ cup of remaining colors. Alternating bags, pipe a variety of stars, dots and rosettes around edge of sponge layer; top with next sponge layer.Repeat process, filling in center of sponge layer with light pink icing and decorating edge of sponge layer, until all layers are complete. For top layer, leave centre of cake plain and pipe stars, dots and rosettes around edge.