Bring a large pot of lightly salted water to a boil. Add macaroni, and cook until tender, about 8 minutes. Rinse under cold water, and drain.
In a large bowl, stir together the carrots, red onion, green pepper, red pepper and celery. Mix in the mayonnaise, condensed milk, sugar, vinegar, salt and pepper. Add the macaroni, toss gently, cover and refrigerate for at least 8 hours. I usually make this a day ahead of time, and stir it occasionally to blend the flavors. The macaroni will absorb some of the liquid.