Color-Cancellation Reflective Technology (CCRT) is based on the fact that, when you look at the display on your phone or laptop, you are actually seeing a mix of emitted light (from the display itself) and ambient light reflected off its surface. Normally the emitted light swamps the relatively subtle reflected component. But by cycling pixels extremely rapidly through a carefully designed sequence of colors, the viewer's brain can be induced to mentally cancel out the emitted component and amplify the reflected light. The result -- a surprisingly realistic, silvery, mirror-like patch in the middle of your display.
I think this is only partially effective for the 4% of the population that has some form of "color blindness".
To see CCRT in action, check it out on the PARC website here.