Preheat oven to temperature indicated on cake mix box directions.
Prepare cake mix as indicated on directions on the box.
Divide cake batter into 5 equal parts in small mixing bowls.
Add different amounts of green food coloring to each bowl of batter from lightest to darkest. One bowl can either be left completely white or just a hint of green. Then each of the other four bowls should be slightly darker than the one before to create 5 layers from lightest to darkest green.
Pour each bowl of batter into a separate cake pan.
Bake the five 6-inch cake pans at the temperature directed on the cake mix box for 18 minutes or until toothpick inserted at the center of cake pan comes out clean.
Remove from oven and cool completely. *It's even better if you can cool the cake layers in the refrigerator for a while so they're more solid when working with them.
Combine vanilla pudding mix with 1 cup cold milk until blended, and then stir in 8 oz Cool Whip. Add a dash of green food coloring to slightly tint the pudding/cream mixture.
Place the darkest cake layer on cake plate. Spread on a layer of Chocolate Fudge Ice Cream Topping, followed by a thick layer of the pudding/cream mixture. Carefully add the second-darkest cake layer, topping with first the chocolate ice cream topping and then the pudding/cream mixture. Continue until all 5 layers have been added and topped with chocolate and pudding/cream mixture.
If desired, top with whipped cream and a maraschino cherry (to look even more like a Shamrock Shake!).