Bring a pot of salted water to a rolling boil, Cook 1 cup macaroni to al dente, according to package directions. Drain pasta, rinse with cold water, and set aside.
In a medium bowl, mix together cooked macaroni, 1/2 cup diced bell pepper, 2 sliced scallions, 1/4 cup shredded carrot, and 1/2 cup diced celery.
Add 5 tablespoons mayonnaise, 2 teaspoons yellow mustard, 1/2 teaspoon sugar, salt, and pepper to bowl. Combine well.
Cover macaroni salad and allow to chill in the refrigerator for 4 hours or overnight.