Food paste (any color desired - from a craft or cake decorating supply store)
Add food coloring to a pan of melting butter.
When the colored butter is melted, pour it over the popcorn as usual.
Nutrition note: The nutritional analysis is based on 12 cups of air popped popcorn and 4 tablespoons of melted butter. Serving size: 3 cups popped.
Calories: 200 Total Fat: 13 g Carbohydrates: 19 g Protein: 3 g