Bring a large pot of lightly salted water to a boil. Cook macaroni until al dente, about 8 minutes. Drain and set aside.
In the same pot, melt butter over medium heat. Whisk in flour and cook for 1–2 minutes to form a roux.
Gradually whisk in milk until smooth. Continue stirring until the sauce thickens, about 3–4 minutes.
Lower heat and stir in cheddar, mozzarella, and cream cheese until fully melted and creamy.
Add shredded chicken, buffalo hot sauce, garlic powder, salt, and pepper. Stir to combine, creating a spicy buffalo cheese sauce.
Fold cooked macaroni into the sauce. Cook for another 1–2 minutes until everything is heated through.
Serve hot, garnished with blue cheese crumbles and chopped green onions for extra zest.