Melt butter in a large pot over low heat. Add marshmallows and stir until completely melted and smooth.
Remove from heat and stir in vanilla extract and orange food coloring until well combined.
Gently fold in Rice Krispies cereal until evenly coated.
Lightly grease your hands with butter or cooking spray. Scoop out the mixture and shape into pumpkin shapes. Use a cookie cutter or free-form the shapes.
Place a green M&M or other green candy on top of each pumpkin as a stem.
Let cool completely before serving. Store in an airtight container at room temperature for up to 3 days.