LAS VEGAS—German carmaker BMW has unveiled the world’s first “colour-changing” car at the Consumer Electronics Show (CES) in Las Vegas. The concept car, called the BMW iX Flow, uses electronic ink technology normally found in e-readers to transform the car’s exterior into a variety of patterns in gray and white. “This is really energy efficient colour change using the technology E Ink,” said BMW research engineer Stella Clarke. “So we took this material—it’s kind of a thick paper—and our challenge was to get this on a 3D object like our cars.” When stimulated by electrical signals controlled by a phone app, the material brings different pigments to the surface, causing the car to take on a different shade or design, such as racing stripes. In the future, the changes would also be controlled by a button on the car’s dashboard or perhaps even by hand gestures, Clarke said. No energy …