Bake and cool four one-layer cakes. Position on foil-wrapped cake boards. Ice cakes smooth with buttercream.
Using Rotary Cutter, cut six strips, 6 in. long x 1/2 in. wide, from Light Pink, Light Blue, Light Yellow and Light Green Sugar Sheets!
Attach the six pink strips to a cake top, leaving 1/2 in. space in between. Repeat with the blue, green and yellow strips for the three remaining cakes.
Using Rotary Cutter, cut four strips, 6 in. long x 3/4 in. wide, from Light Pink, Light Blue, Light Yellow and Light Green Sugar Sheets!
Create a border by attaching the four blue strips to the corners of the cake with pink strips. With piping gel. Repeat for the yellow strips (blue strips), pink strips (green strips) and green strips (yellow strips).
Using the letters from the cookie cutter set and black FoodWriter, trace letters on the back side of the Sugar Sheets! colors. Cut out with scissors.
Using piping gel, attach green letter to the yellow border cake, the blue letter to the pink border cake, the pink letter to the green border cake and the yellow letter to the blue border cake.
Using punch with Small Circle Cutting Insert, cut 16 circles from White Sugar Sheets! Attach to the corners of the cakes with piping gel.
Finish the cakes by using tip 5 and white buttercream to pipe a bead border at the bottom.