E-ink with color is just one of many different extreme power efficient color display tech forthcoming years.
Samsung aquired Philips spin-off display company Liquavista in january 2011 especially suitable for E-book readers.
American company GammaDynamics is another interesting color display tech.
Pixtronix another one that Qualcomm aquired during autumn 2011.
Mirasoldisplay is another extreme display tech that is an IMOD tech that Qualcomm have aquired some years before.
So it is some different color display techs that is suitable for E-book readers out there!