Cook the elbow macaroni according to package instructions. Drain and rinse under cold water to cool. Set aside.
In a large bowl, combine the shredded green cabbage, grated carrots, shredded red cabbage, and chopped green onions.
In a separate bowl, whisk together the mayonnaise, apple cider vinegar, sugar, Dijon mustard, garlic powder, salt, and pepper until smooth.
Add the cooled macaroni to the vegetable mixture and pour the dressing over it. Toss everything together until well combined.
Cover the salad and refrigerate for at least 1 hour to allow the flavors to meld.
Serve chilled and enjoy!