Make cake and cupcakes. Prepare batter for cake and cupcakes. Bake and cool cake and cupcakes. Cake is two-layers cake, 4 in. tall. Place cake on foil-wrapped cake circle.
Decorate cake. Prepare buttercream icing following recipe directions. Tint yellow, green, blue and rose.
Use spatula and yellow icing to ice cake smooth. Use tip 12 and green, blue and rose icing to pipe dots on cake sides. Use tip 3 and yellow icing to pipe bead bottom border.
Decorate cupcakes. Use tip 1M and rose, blue and green icing to pipe swirls on tops of cupcakes.