Bring a large pot to boil and add elbow macaroni. Cook until al dente and then rinse in a colander in cold water.
In a large bowl add pasta, tuna, carrots, red onion, bell peppers, and avocado. In a small bowl whisk mayonnaise, cider vinegar, sugar and dijon mustard. Pour over pasta and toss to coat. Garnish with fresh cracked salt and pepper and chopped chives if desired. Serve immediately or chilled, but add avocado in right before serving.