Preheat the oven to 350°F (175°C) and grease a 9x13-inch pan. Bake brownies according to package instructions, approximately 25-30 minutes, then cool completely before cutting into cubes.

In a large bowl, whisk together the instant vanilla pudding mix and cold milk for about 2 minutes until thickened. Add green gel food coloring until desired color is reached, then let sit for 5 minutes.

Crush Mint Oreo cookies in a zip-top bag until you have a mix of fine crumbs and small chunks.

In a trifle bowl, layer half the brownie cubes, then half the pudding, half the whipped topping, and half the crushed Oreos.

Repeat with remaining ingredients, creating a layered effect.

Cover with plastic wrap and refrigerate for at least 4 hours, preferably overnight.

Before serving, garnish with remaining crushed Oreos, a dollop of whipped topping, and optional green sprinkles.