Make up the cake mix according to manufacturer’s instructions. Measure out 3 pounds batter, deposit 1 pound 8 ounces into a sprayed and papered 8-inch cake pan. Repeat again to make 2 cakes total. Bake at 350F until cake springs back lightly when touched. Let cool completely. Once cooled, trim the bellies of each cake, saving them for other uses. Place one cake round on a cake board, and fill with buttercream. Place the other round on top and crumb coat with buttercream. Place buttercream in 3 bowls, color one orange, using a drop or two of brown to mute the color. Repeat with the pink and purple, also muting slightly with brown. Place each colored buttercream in a different size and style star tip, also making a white buttercream bag. Smooth ice with white buttercream. Pipe a very small amount of each color around the sides and top of the cake and smooth ice again to swirl the colors. Trace a waning moon on the top of the cake and fill in with different sizes and colors of rosettes. Top with white sprinkles just on the rosettes.