Preheat the oven to 350 degrees F.
In a medium skillet, melt the butter over medium heat. Add the red bell pepper and cook for 3 minutes. Stir in the shrimp and green onions and cook until the shrimp are pink and firm, 2 to 3 minutes. Stir in the sour cream, cheeses, and mayonnaise. Add the salt and pepper, to taste. Spoon the mixture into a 2-quart baking dish. Bake until lightly browned and bubbly, 30 to 35 minutes. Serve with assorted crackers.