In 4-quart saucepan, heat milk over medium-high heat until steaming and bubbling around edges. Stir in 1 cup of the Cheddar cheese, the Monterey Jack cheese, Velveeta™ cheese and seasoning mix. Continue to cook over medium-low heat 4 to 5 minutes, stirring frequently, until cheese is melted and sauce is smooth; remove from heat. Add cooked macaroni to cheese sauce, stirring to coat. Stir in chicken, tomatoes and green chiles until well mixed; transfer to baking dish.