Bring a large wide pot of salted water to a boil. Add the pasta and cook as the label directs. Reserve 1/2 cup cooking water, then drain.
Melt the butter in the pot over medium heat. Whisk in the flour, mustard powder and paprika; cook, whisking, until smooth and slightly darker, about 1 minute. Slowly whisk in the milk and continue to cook, whisking occasionally, until the sauce thickens slightly and comes to a simmer, 7 to 8 minutes. Whisk in the cheddar, American cheese and cream cheese until melted.
Add the pasta to the sauce; toss, adding the reserved cooking water as needed to loosen. Season with salt.
Photograph by Ryan Liebe