Heat a medium saucepan over medium-high heat. Coat pan with cooking spray. Add onion, bell pepper, and garlic; sauté 4 minutes. Add curry paste and red pepper; cook 1 minute, stirring constantly. Stir in broth and coconut milk; bring to a boil. Reduce heat, and simmer, uncovered, 20 minutes, stirring occasionally. Add shrimp; cook 4 minutes or until shrimp are done. Stir in spinach; cook 2 minutes or until spinach wilts.