Preheat the oven to 375 degrees. Line two baking sheets with parchment paper.
Using an electric mixture, mix the butter and sugars together until completely blended.
Add in the egg and the vanilla. Slowly add in the green food coloring until the perfect color is formed.
Mix in the flour, baking soda, and salt by hand. Overmixing can cause the cookies to flatten.
Fold in the M&Ms , and scoop the cookie dough onto the parchment paper. Place some extra M&Ms at the top.
Bake for 8-10 minutes, and enjoy.