In a large bowl add the green and purple cabbage, carrots, green onions, rice vinegar, mayonnaise, sugar, salt and pepper. Stir together all ingredients until completely combined.
Give the coleslaw a quick taste to see if you prefer more salt or a bit more sugar.
Serve chilled as a side dish, snack or add to a sandwich instead of lettuce. This coleslaw is best when served within 2 hours of making it.