For sauce, melt butter or margarine in another medium saucepan over medium-high heat. Add onion, sweet pepper, and garlic; cook and stir for 3 minutes or until onion is tender. Add flour; cook and stir 1 minute more. Add milk, half-and-half, or light cream; cook and stir for 3 to 5 minutes or until sauce has thickened slightly. Remove from heat. Add salt, ground black pepper, and ground red pepper to taste.