Using 1 cake layer on the cake board, scoop 1 C of frosting onto the top of the cake and spread evenly
Sprinkle ¾ C of lucky charm cereal all over the frosting layer
Place the second layer of cake on top of the first layer of cereal frosting.
Scoop another 1 C of frosting onto the second layer of cake and spread evenly.
Sprinkle another ¾ C of lucky charms
Place the last layer of cake on top
Frost entire cake with the remaining white frosting
Scoop ¼ C of each colored frosting into their own bags, set aside
Using a knife, blot dollops of the colored frosting all over the side of the cake
Take a flat spatula and lightly spread the colored frosting to create a rainbow effect
Pick out the marshmallows from the cereal and place the randomly on the sides of the cake
Using the colored frosting, pipe dollops of the frosting on top
Fill the center of the cake with Lucky Charm cereal
Cut and enjoy!