Blueprint is a copy of the original drawing that shows how to construct a machine, a building, or another object. The original is called a mechanical drawing. Drafters use special photographic processes to make copies of a mechanical drawing. The copies are called blueprints because the oldest of these processes produces drawings with white lines on a blue background. Over the years, other photographic processes have been developed that create copies with dark lines on a white background. People use the term blueprint, however, to refer to any copy of a mechanical drawing, regardless of the color of the background.