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 is needed to maintain the colour the driver selects, according to BMW.

"My favourite use case is the use of colour to influence sunlight reflections," said Clarke. "On a hot, sunny day like today, you could switch the colour white to reflect sunlight. On a cold day, you could switch it black to absorb the heat."

Though the vehicle displayed at CES could only alternate between grey and white, the technology will be expanded to cover a spectrum of colour, according to BMW. -BBC