Prepare 3 boxes white cake mix following package instructions; divide in thirds
In one portion of batter, gently stir in Royal Blue Icing Color to desired shade (use clean toothpicks to transfer color from jar to batter). Repeat with Lemon Yellow and Golden Yellow Icing Colors to color second portion. Reserve 1 portion batter white.
Place Batter Dividing Ring in the first prepared 9 x 1 1/2 in. pan. Pour blue-colored batter in outer section and yellow-colored batter in the middle section and white in center section. Fill sections halfway.
Remove ring from pan by carefully lifting straight up on handles. Rinse and completely dry ring.
Place ring in 2nd prepared pan and in the first prepared 9 x 1 1/2 in. pan. Pour white batter in outer section and blue-colored batter in the middle section and yellow-colored batter in center section. Fill sections halfway.
Remove ring from pan as before. Bake and cool cakes following recipe directions. Remove and stack cakes.
Place clean and dry ring in 3rd prepared pan. Pour yellow-colored batter in outer and white colored batter in the middle section and blue-colored batter in the center section. Fill sections halfway.
DO NOT PUT DIVIDING RING IN OVEN.
Bake and cool graduation cap cookie using roll out cookie recipe. Prepare Color Flow Icing, divide and tint portions blue and yellow. Using tip 3 and full strength blue color flow icing, outline cookie. Flow in with thinned icing in a cut parchment bag. Let dry. Using tip 3 and full strength yellow color flow icing, pipe tassel. Let dry and set aside.
Prepare buttercream icing, divide and tint portions blue and yellow, reserve white. Assemble cake layers on foil-wrapped cake board, spreading thin layer of buttercream icing between layers. Spatula ice cake smooth. Using tip 3 and white icing, pipe swirls on cake sides. Using tip 18 and blue icing, pipe stars on cake sides. Using tip 6 and yellow icing, pipe top and bottom bead borders. Position cookie on cake top, securing with a swirl of buttercream icing.
*Combine Lemon Yellow and Golden Yellow Icing Colors for yellow shown