Place fillets on a greased baking sheet. Sprinkle with salt, pepper and cayenne. Bake, uncovered, at 350° for 15-20 minutes or until fish flakes easily with a fork. , Meanwhile, in a large skillet, saute onion and green pepper in oil until tender. Add garlic; cook 1 minute longer. , Flake fish with 2 forks; set aside. In a large bowl, combine the hot enchilada sauce, green enchilada sauce, sour cream, mayonnaise, chiles, onion mixture and fish. Spread 1/2 cup mild enchilada sauce into each of 2 greased 13x9-in. baking dishes. Sprinkle each with 1 cup cheese. , Place a heaping 1/3 cup halibut mixture down the center of each tortilla. Roll up each and place seam side down over cheese. Pour remaining sauce over top. , Cover and bake at 350° for 30 minutes. Sprinkle with the green onions, olives and remaining cheese. Bake, uncovered, for 10-15 minutes longer or until cheese is melted.