SPRAY large nonstick skillet with cooking spray. Add peppers and onion; cook and stir on medium-high heat 5 min. or until crisp-tender. Remove from skillet; set aside.

BEAT whole eggs, egg whites and water with wire whisk until well blended. Pour into skillet; cover. Cook 6 min. or until egg mixture is set but top is still moist. As egg mixture sets, lift slightly with spatula to allow uncooked portion to flow underneath.

TOP with pepper mixture and cheese. Slip spatula underneath, tip skillet to loosen and gently fold omelette in half. Cover; cook 3 min. or until cheese is melted. Serve topped with the salsa.