LCD's would be a lot more comfortable to read if they reflected light, rather than emitting it. They'd be like reading paper. They also wouldn't consume the power of a backlight. Admittedly you'd need a backlight for low-light conditions, but that can easily be achieved.

The traditional model of red, blue and green subpixels juxtaposed next to eachother wouldn't work, because even a pure white signal would only reflect 1/3rd of the incident light. Or less. What you need is

-A material that's transparent or filters blue depending on electric signal.
-A material that's transparent or filters green depending on electric signal.
-A material that's transparent or filters red depending on electric signal.

You then sandwich these materials in three layers for each pixel. If they're not really thin, viewing might be a little awkward from an angle. Behind this whole array is simply a pure white, non-shiny surface. Either that or a one-way mirror, for backlight conditions. (Can you have a one-way frosted mirror?) There may be a trade-off between required backlight power and percentage of reflectivity. That is, of course, unless you can make the pure white background also responsive to electricity.