Place chicken in a 3-qt. slow cooker. Top with mangoes, onion, red pepper and garlic. In a small bowl, combine the pineapple juice, orange juice, soy sauce, chili sauce and pepper; pour over chicken. Cover and cook on low 4-5 hours or until chicken is tender.
Remove chicken mixture to a serving platter; keep warm. Transfer cooking juices to a small saucepan. Bring juices to a boil. Combine cornstarch and water until smooth; gradually stir into the pan. Bring to a boil; cook and stir until thickened, about 2 minutes. Serve with chicken mixture, rice and green onions.
