Lightly crush 2 cups of caramel popcorn and mix with the uncrushed popcorn.
Add the butter and marshmallows to a microwave-safe bowl. Microwave on high until hot and the marshmallows are beginning to melt, 1 minute 30 seconds to 2 minutes. Stir very well until completely combined.
Add the food coloring to get the desired bright green color (we used 10 drops yellow and 1 drop green) and stir until evenly distributed.
Add the popcorn and stir very well to completely coat.
Serve immediately or place in a small slower cooker on low heat to stay warm.