Bring a large pot of salted water to a boil. Add the pasta and cook according to the package directions until al dente. Drain the pasta and rinse with cold water to stop the cooking process.
In a large bowl, add the diced red bell pepper, chopped celery, and diced red onion. Then add the cooked pasta and shredded chicken.
In a small bowl, whisk together the low-fat mayonnaise, plain Greek yogurt, Dijon mustard, fresh lemon juice, salt, and black pepper. Adjust seasonings as needed. Pour the dressing over the pasta mixture and gently toss until well combined.
Cover the bowl and refrigerate for at least one hour before serving. Stir again before serving to ensure the flavors meld. Garnish with parsley.