Will consumers sacrifice "green" e-paper on the altar of fast color, relegating the nascent technology category to a niche? For the analysts who track the display market, the question is a page turner, and they're of a mixed mind on the likely conclusion.

E-paper displays can replace virtually any printed page with a nonvolatile image that is changed electronically. Beyond e-paper versions of books and periodicals, developers envision applications for blueprints, maps, shelf labels, signage, smart cards and even "skins" that cover your iPhone with changing patterns.

E Ink's Vizplex display uses microcapsules containing white and black pigments that can be attracted to the surface with electrical potentials to form paperlike white, black or grayscale pixels.

For green paper replacement, the e-paper display must retain its image without any energy being expended (called zero-power or bistable mode). That capability and the lack of a backlight requirement are how e-book readers maintain their long battery lifetimes--which are sometimes measured in page turns, since energy is expended only when the displayed image changes. (LCDs, by contrast, run down a battery in a few hours, regardless of what is being displayed.)

The e-paper category today is dominated by e-books using E Ink's Vizplex display, which looks remarkably like a clean, white sheet of paper printed with black ink. "Vizplex is widely used today for its best-of-breed whiteness and because it is already being mass produced," said Gartner analyst Amy Tang, who tracks the e-paper market.

Most other bistable display technologies bounce ambient light off a highly reflective surface, making text look like it is written on a mirror. The paperlike appearance of E Ink's Vizplex is the result of bouncing ambient light off the same white and black pigments that are used in traditional inks; in the Vizplex, the pigments fill the charged microcapsules that form the display pixels.

E Ink's monochrome display (no color yet) commands at least a 20 percent price premium over other e-paper solutions. It handles page refreshes fast enough for menus, windows and simple animations, but it cannot display live video. About two dozen independent development efforts worldwide are working to address the Vizplex's shortcomings. But E Ink itself makes no apologies for its success.