Spray a 9x13-inch glass baking dish with cooking spray. Lay slices of bread in the bottom of the prepared pan in a single layer, trimming and filling in gaps as necessary. Spread 1 cup Cheddar cheese, onion, green bell pepper, yellow bell pepper, red bell pepper, and bacon on top, in that order. Whisk eggs, sour cream, mustard, seasoning blend, salt, and pepper together in a bowl until well combined. Pour mixture over bread, making sure to soak the top layer. Cover baking pan and refrigerate strata at least 8 hours. Preheat the oven to 350 degrees F (175 degrees C). Uncover strata and bake in the preheated oven for 45 minutes. Sprinkle remaining Cheddar cheese evenly on top and return to the hot oven. Bake until Cheddar cheese is melted, 10 to 15 minutes more. Let strata stand 5 minutes before serving.