In 1-quart saucepan, heat bell pepper, bouillon and water to boiling over high heat. Remove from heat; stir in couscous. Cover; let stand 5 minutes. Stir in onions; set aside; transfer half of mixtue to a small microwavable bowl.
Meanwhile, line broiler pan with foil; spray with cooking spray. Place chicken breast halves on pan. Broil 4 to 6 inches from heat 5 minutes. In small bowl, mix preserves and mustard; transfer half of mixture to a small microwaveable bowl.
Turn chicken. Brush chicken with half of preserves mixture; discard any remaining. Broil 3 to 5 minutes longer or until chicken is fork-tender and juices run clear.
Stir couscous mixture lightly with fork; divide evenly onto 2 individual serving plates. Top each with chicken. Stir water into remaining preserves mixture. Microwave on High 20 to 40 seconds or until warm; spoon over chicken. If desired, garnish with additional sliced green onions.