01 - Preheat your oven to 375°F (190°C). Slice the tops off the orange bell peppers and meticulously remove all seeds and membranes. Reserve the tops for a decorative touch. Lightly coat the interior and exterior of each pepper with olive oil, then season sparingly with kosher salt and freshly ground black pepper. Arrange the peppers upright in a baking dish. Roast for 20 to 25 minutes, or until they are tender yet maintain their structural integrity. Remove from the oven and set aside.
02 - Concurrently, cook the elbow macaroni in a large pot of generously salted boiling water according to the package directions. Once cooked to al dente, drain thoroughly and set aside.
03 - In a medium saucepan, melt the unsalted butter over medium heat. Incorporate the all-purpose flour and whisk continuously for 1 to 2 minutes to establish a smooth roux. Gradually introduce the whole milk, whisking constantly to prevent clumping, and continue to cook until the mixture thickens and begins to bubble gently, approximately 3 to 5 minutes.
04 - Reduce the heat to low. Add the shredded cheddar, mozzarella, and Monterey Jack cheeses to the sauce, stirring until completely melted and the sauce is uniformly smooth. Stir in the smoked paprika, cayenne pepper (if using), garlic powder, and mustard powder. Season with salt and freshly ground black pepper to your preference.
05 - Gently fold the cooked macaroni into the cheese sauce, ensuring each piece is evenly coated. Carefully spoon the macaroni and cheese mixture into the pre-roasted pepper bowls. Place the reserved pepper tops back onto the filled peppers to achieve a festive pumpkin appearance.
06 - Present the Halloween Orange Mac and Cheese Bowls immediately. For an enhanced presentation, consider garnishing with chive "stems" to amplify the Halloween theme.