Prepare and bake cupcakes as directed on the package. Cool completely.

Add green food coloring to a tub of frosting and mix well. Place into a piping bag fitted with a 1M tip. Set aside.

Use a melon baller to scoop a hole into the center of cupcake and reserve the top cake piece. Scoop a little more out and discard that cake. Fill with marshmallows and rainbow sprinkles and replace reserved top.

Pipe frosting onto each cupcake and sprinkle with sprinkles. Serve immediately or store covered until ready to serve.