It basically similar to one of those E book reader screens the whole car is wrapped in. it sends an electric charge through the wrap that causes the particles or the pigment to group together differently. It's sort of like magnetic ride suspension but for color. Well not color as it's only light and dark for now but you get the idea lol
In addition to personalization, a variable exterior also contributes to the efficiency of the vehicle. By nature, a white exterior on hot days would reflect sunlight and conversely, a black exterior on cold days would absorb the sunlight. This could reduce the amount of energy the vehicle uses for heating and cooling the interior.
The process of changing the color of the car is extremely efficient because of E Ink’s ultra-low power technology. E Ink’s digital paper is bistable – meaning it only uses power to change color, not to maintain it. This inherent trait makes it possible to change the color of the car with minimal power, and aligns with the sustainability mission of the all-electric vehicle.
“This concept car with BMW is an amazing display of how surfaces of the future will transform to personalize, customize and provide information,” said Tim O’Malley, AVP, US Regional Business Unit. “Because E Ink is incredibly low power and durable, we can put our display technology on almost any surface, transforming a once static space into something dynamic and spectacular – and sustainable.”
Most displays emit light. E Ink does not – it reflects ambient light in its surroundings. This gives the display a paint-like appearance and a natural visual experience. The electronic ink is made up of millions of tiny microcapsules that are filled with white and black pigments – the same ink pigments used in the printing industry today. These pigments can be moved up or down using an electric field in a controlled manner, thereby changing the appearance at the surface of the display.