The correct answer is B) red. According to the United States Coast Guard regulations, a triangular daymark would be colored red. This is because red daymarks are used to mark the port (left) side of a navigable channel or waterway. The triangular shape is a standard design for port-side daymarks, which help to visually indicate the proper side for vessels to pass. The other answer choices are incorrect because: A) red and white is the color scheme for starboard (right) side daymarks, C) green is used for starboard side daymarks, and D) green and white is the color scheme for channel centerline or fairway daymarks, not port-side daymarks.