In a large saucepan, melt together peanut butter and marshmallows. Stir in vanilla extract and food coloring.
Remove pan from heat. Quickly stir in corn flakes until coated and blended.
Remove about 1/2 cup of corn flake mixture at a time. On a silicone mat (or parchment paper), form mixture into trees. Using a flat-edge or butter knife helps form the sides. Add M&Ms as ornaments.