Preheat oven to 350°. In a 13x9-in. or 2-1/2-qt. baking dish, combine broth and grits. Bake, uncovered, until liquid is absorbed and grits are tender, 30-35 minutes., Stir in tomatoes, Monterey Jack cheese and 1/2 cup cheddar cheese. Bake, uncovered, until heated through, about 10 minutes. Sprinkle with pepper and remaining cheese; let stand 5 minutes., In a large skillet, heat butter over medium-high heat; saute green pepper and onion until tender, 6-8 minutes. Add shrimp and garlic; cook and stir until shrimp turn pink, 2-3 minutes. Spoon over grits.