Changing the paint color on your car is a time-consuming affair - your workshop mechanics will need to go through a whole lot of disassembly and prep work, not to mention lengthy amounts of time in a spray booth followed by hand blocking sessions where you could grow a 10-foot beard by then. There is a new technology being developed that makes color change a simple affair of twisting a knob. This variable-color paint involves a special polymer coating that has paramagnetic iron oxide particles in it, changing their alignment whenever a current passes through the coating, which results in a different way light is reflected - and voila! Your eyes will see a different color.

Source: Autoblog Green