Mix salt, dry mustard, garlic powder, paprika, onion powder, white pepper, and black pepper in a small bowl.
Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally until cooked through but firm to the bite, 8 minutes. Drain and rinse macaroni under cold water until cooled.
Whisk mayonnaise, sour cream, and evaporated milk in a large salad bowl until dressing is smooth and creamy; stir in seasoning mix until well blended. Mix macaroni, onion, green, red, and yellow bell pepper, celery, and carrots into the dressing until thoroughly coated.