Southern Celery Mac N Cheese

Name: Southern Celery Mac N Cheese
Ingredients: 2 cups macaroni pasta; 4 tablespoons butter; 4 cups sliced celery; 3 tablespoons all purpose flour; 1 teaspoon salt; 1 cup milk; 1 small carton sliced mushrooms; 2 tablespoons chopped bell pepper; 2 tablespoons chopped red bell pepper; 2 cups shredded cheddar cheese; 1 cup bread crumbs; 2 tablespoons butter melted