Prepare buttercream icing. In small bowl mix together yellow, purple and green nonpareils. With spatula, ice top pentagon with buttercream. Place cake over cookie pan. Gently press handfuls of nonpareils to iced section of cake. Repeat with side of cake, icing and decorating one section at a time.
Helpful Hint: Raise cake up on a sturdy bowl to make it easier to apply nonpareils to bottom of cake.
Lightly crumb coat remainder of cake. Prepare decorating bag with tip 6 and buttercream icing. Outline edges of pentagon shapes, then pipe vertical lines to fill in remaining pentagons.
Makes 12 servings.