In a large mixing bowl, combine cream cheese, cheddar cheese, and Parmesan cheese until well blended.
Add in green onions, diced red bell pepper, garlic powder, onion powder, and walnuts; mix until evenly distributed.
Gradually add orange food coloring, mixing until the desired pumpkin color is achieved.
Shape the cheese mixture into a ball and wrap it in plastic wrap; refrigerate for at least 2 hours to firm up.
Once chilled, unwrap the cheese ball and roll it in chopped walnuts for a textured exterior.
Place the cheese ball on a serving platter and garnish with parsley to resemble a pumpkin stem.
Serve with an assortment of crackers, veggie sticks, or pretzels for dipping.