Prepare yellow cake mix according to bag directions. Scale 2 lbs batter into sprayed 10” baking pans, repeat at least 2 more times to make 3 cakes total. Bake at 350°F for 40-45 minutes or until cake springs back lightly when touched. Let cool completely and depan. Stack, fill, and crumbcoat with white buttercream. At the base of the cake, pipe a ring of light blue buttercreme. Combine white and light blue buttercreme icings, creating lighter blue colors as the rest of the cake is iced. Create a lighter yellow color by using a ratio of 1 part Bright Yellow to 5 parts White buttercreme. Using russian tips, load piping bags using a combination of the rest of the buttercreme colors, combining colors in each bag as desired. Pipe a ring of flowers around the top edge of the cake, fill in with light green buttercreme leaves.