Preheat oven at 350 degrees. Spray 9x13 baking dish with cooking spray.
Make cake mix per directions on the back of the box. (Ingredients ask for egg whites, oil and water). Add in 2 tsp of mint extract and food coloring.
If you want really green add 50 drops of color. Or you can use food coloring paste just add your desired color.
Pour batter into baking dish and bake as directed for time listed on the back of cake mix box. Oncethe cake is done, allow the cake to cool ccompletely.
Spread hot fudge sauce on cooled cake. ( If the hot fudge sauce is too hard to spread at room temperature, put it in the mircowave with lid removed for about 15 to 20 seconds. Stir with spoon until you get a spreadable consistency. Make sure it's not too hot and liquidity. Make sure your fudge layer is completely cool before adding whipped topping).
Add in 1/2 tsp of mint extract and green food coloring ( about 6-10 drops) to the whipped topping. Mix well. Spread whipped topping onto cake. Sprinkle with chopped creme de menthe chocolate candies. This cake will need to be refrigerated until serving time.