The phrase "red leather upholstery" refers to a type of interior car or furniture trim that is made from red-colored leather. Leather is a durable and luxurious material often used in high-end cars, furniture, and decor because of its rich appearance and long-lasting nature. In this context, "red" refers to the color of the leather, which can range from a deep burgundy shade to a bright scarlet hue. The term "upholstery" describes the process of covering furniture or car seats with leather material for added comfort and style. So, when put together, "red leather upholstery" refers to red-colored leather used as a cover material on furniture or in cars.