In a stand mixer, combine the butter, powdered sugar, heavy cream, and cotton candy extract until smooth. Separate into two medium-sized bowls and one small bowl. Fold in pink and blue food coloring into two medium-sized bowls and purple food coloring in the small bowl of frosting. Add to piping bags and set aside.
Stack 4 round cakes on top of each other, spreading a small amount of frosting in between each layer. Using any excess frosting (or whipping up more), add a light coat to the sides and the top of the cake. Refrigerate for 10 minutes to set
Pipe large dollops of pink and blue frosting on the sides and top of the cake and smooth together with an offset spatula. Add small dollops of purple and smooth until the cake is covered in the watercolor frosting.
Top the cake with lollipops, rock candy, candy sticks, and cotton candy. Press sprinkles into the bottom third of the cake and garnish with silver leaf. Enjoy!