A 3-color ink-concept is being developped:
http://www.engadget.com/2007/09/06/o...er-technology/
From their website the only downside is that it will use power when the image is static...
1. Full color display from single material for low materials and production cost.
2. Meet signage needs in size from shelf edge to highway billboards.
3. High brightness, peak reflectivity up to 95%.
4. Low power consumption.
1. Low voltage and current during switching.
2. Minimal power consumption when image is static.
5. Sub-second switching speed.
6. Heat management through controllable IR reflectivity.
7. Applicable on rigid or flexible substrates.
8. Lightweight, rugged, durable, and damage tolerant.
9. Costs scales only linearly with size.