Prepare a baking sheet by lining it with parchment paper or wax paper. Set aside.
In a medium saucepan, combine granulated sugar, unsalted butter, milk, and unsweetened cocoa powder. Heat over medium heat, stirring frequently, until it comes to a boil. Let it boil for 1 minute, stirring constantly.
Remove the saucepan from heat. Stir in creamy peanut butter, vanilla extract, and peppermint extract until smooth and peanut butter is melted.
Add quick oats to the mixture and stir until well combined.
If using green food coloring, add a few drops and stir until evenly distributed.
Drop spoonfuls of the cookie mixture onto the prepared baking sheet. Flatten slightly with the back of a spoon.
Optionally, sprinkle chocolate chips or mint chips on top of each cookie while still warm.
Allow the cookies to cool and set at room temperature for 30 minutes to 1 hour, or refrigerate to speed up the process.
Once set, store any leftovers in an airtight container.