So, since May 2011 there is an E Ink display with the b/w resolution of 2400 x 1650 px, so actually one could build a color device with the resolution of today's b/w ereaders 1200 x 825 = 2400/2 x 1650/2 (reduction because of the 2x2 color filter matrix)
:
http://goo.gl/LVIyc
http://goodereader.com/blog/e-reader...en-technology/
http://www.engadget.com/2011/05/19/e...ds-radios-the/