Cook the penne pasta in a large pot of salted water according to package directions until al dente. Reserve 1/2 cup of pasta water before draining.
While the pasta cooks, add the cream cheese, buffalo sauce, ranch dressing, chicken broth, garlic powder, paprika, and black pepper to a large skillet over medium heat. Whisk until the cream cheese melts and the sauce is smooth and creamy.
Stir in the shredded cheddar and mozzarella cheese until melted and incorporated into the sauce.
Add the shredded chicken to the sauce and stir to coat evenly. Reduce the heat to low and let simmer for 5 minutes.
Add the cooked and drained pasta to the skillet with the sauce. Toss gently to coat, adding reserved pasta water a little at a time if needed to thin the sauce. Continue tossing until the pasta is evenly coated.
Serve the buffalo chicken pasta hot garnished with sliced green onions and crumbled blue cheese. Enjoy!