1. Prepare the grill or broiler.
2.For sauce: combine allspice, basil, nutmeg, cinnamon, thyme, cayenne pepper, brown sugar, salt and pepper. Mix well. Slowly whisk in the oil, soy sauce, vinegar, orange juice and lime juice. Stir in the peppers, onions and scallions and mix thoroughly. Simmer for about 10 minutes over medium heat.
3. Sprinkle shrimp with salt and pepper and grill or broil until done. Toss shrimp with the sauce and serve immediately.