Heat a large Dutch oven over medium-high heat. Coat pan with cooking spray. Add onion, bell pepper, celery, and garlic; sauté 5 minutes or until tender. Add potato and next 5 ingredients (potato through tomato paste). Bring to a boil; cook 5 minutes. Stir in salt, black pepper, and shrimp; cook 5 minutes or until shrimp are done. Sprinkle with green onions.