The display is a passive-matrix, reflective type cholesteric liquid crystal display. Two 3.8-inch diagonal QVGA prototypes, a monochrome display and a color version able to display 512 colors, were shown.
Differing from widely used flat displays that have color filters consisting of red, green and blue pixels, the paper display has a three layered structure in total about 0.8 mm thick. One layer consists of two 0.125 mm-thick films sandwiching liquid crystal. Cholesteric crystals in each layer are twisted in a certain pitch to reflect only red, green or blue light respectively.
Images on the screen can be changed with 10-milliwatts to 100-milliwatts depending on scanning speed.
(Thanks to John for the link…)