Coat a 3-quart casserole dish with cooking spray; set aside.
Cook macaroni in salted water as directed on package; set aside.
Melt butter in a medium saucepan over medium-low heat.
Slowly add flour, stirring constantly; cook for about 3 minutes.
Slowly whisk in milk to thoroughly incorporate flour mixture.
Stir in onion, paprika and bay leaf.
Simmer for 15 minutes, stirring frequently; remove from heat.
Combine blue cheese with about two-thirds of both types of cheddar cheese in saucepan and season to taste with salt and pepper; stir in macaroni. Pour half of macaroni mixture into prepared casserole dish and top with remaining cheddar cheeses.
Pour in remaining macaroni mixture and sprinkle with Parmesan cheese; bake for 30 minutes.
Let stand for about 5 to 10 minutes before slicing into 9 pieces.