In a kettle, combine chicken, onions, and bell peppers. Cook over medium high h eat, stirring occasionally, until chicken is no longer pink. Add water, tomato sauce, stewed tomatoes, chili powder, salt, and black pepper. Continue cooking, stirring occasionally, until chili comes to a boil. Add mixed vegetables and p asta. Reduce heat to medium low. Continue cooking, stirring often, until flavor s are blended, 20 minutes.