This is not the traditional King Cake, but more like a Mardi Gras decorated two-layer cake.
Make the cake with the above ingredients but use 2 whole eggs instead of three egg whites. Follow the rest of the box directions. Bake the cake, using 2 round cake pans that have been fitted with parchment paper that has been cut to size to fit in the bottom of the pans. Lightly spray the sides of the pans before pouring in the cake mix, dividing equally between the 2 pans. Bake according to the box directions.
Let the cakes cool for about 10 minutes before removing one to your serving plate, top side down. Carefully peel off the parchment paper from the bottom which is now on top. Cool completely before spreading the lemon creme onto the bottom layer.
Carefully remove the other cake layer onto another plate or your hand, removing the parchment paper from the bottom. Flip this cake layer over, and place the bottom next to the lemon creme.
Frost the sides and top of the cake with the cream cheese frosting.
To make the decorating icing, mix the powdered sugar, very soft butter, vanilla and half the listed milk together. Slowly add more milk, 1 teaspoon at a time, until a spreadable icing consistency is achieved.
Divide the icing into 3 different small bowls. Add a few drops of green food coloring to one and mix. Add a few drops of yellow food coloring to another and mix. Add a few drops of blue and red food coloring to another to make purple.
With a pastry bag fitted with a flower tip, carefully spoon the icing into the side of the bag, trying to get all 3 colors to get in the tip at the same time. You could also use a tall glass for this purpose.
Decorate around the parameter of the bottom and top of the cake with the flowers.
Using a piece of cardboard cut to size, section off the top of the cake to use the 3 colors of sugar as shows in the image. If your icing is really soft, you might need to hold the cardboard rather than place it on the icing to prevent dents.