The tarpon has this kind of mouth. It feeds near the surface. A sub-terminal mouth is on the underside of the head. Fish with this type of mouth usually feed on the bottom. The bonefish has a sub-terminal mouth.
Some fish have specialized mouths.
Red is a common color in fish. You might think that red fish would be very easy for a predator to find. In deep water red light is filtered out quickly so red is a good camouflage. At night red-colored objects appear gray. The squirrelfish has this kind of coloration.