Melt butter in a large pot. Add marshmallows and stir until melted.
Stir in food coloring.
Stir in cereal.
Working quickly, use a greased 1/4 cup measuring cup to dump the cornflake mixture in mounds on a cookie sheet lined with parchment paper. Use your fingers (grease them well) to form the mounds into wreath shapes.
Decorate with red M&Ms before they set.
Let cool completely and store in an airtight container.
Notes
Nutritional info is provided as an estimate only and will vary based on brands of products used.