Preheat oven according to brownie mix instructions, usually 350°F (175°C). Grease a square baking pan and prepare brownie mix as directed. Bake for 20-25 minutes until a toothpick comes out clean. Cool completely on a wire rack.

In a bowl, whisk together pudding mix with milk according to package directions. Blend for 2 minutes until smooth. Add green food coloring and mix until achieving a vibrant hue. Set aside.

Crush mint Oreos in a Ziploc bag until they are coarse pieces. Set aside for topping.

Layer trifle by cutting cooled brownies into bite-sized pieces. In a clear bowl or cups, layer brownie pieces and then a scoop of green pudding. Repeat until filled. Top with Cool Whip.

Sprinkle crushed Oreos on top of Cool Whip. Optionally add mint leaves or chocolate shavings.

Cover with plastic wrap and refrigerate for at least 2 hours before serving.