Joe Levi from PocketNow just wrote good article which topics is about Android phones screens and battery usage. He points that using red rather than white lighting at night can help preserve your "night-vision" and the consequence of using only the red-subpixels on OLED displays can dramatically decrease power usage of the screen. As you know the number one power hog on any Android device is the screen, so by improving it you can a longer battery life.

Android phones with OLED displays include the Nexus One, Droid Incredible, Samsung Galaxy, and others. OLED, which stands for "Organic Light Emitting Diode", displays have separate subpixels for each color (red, green, and blue). The basis of this hack is founded upon the theory that each color channel has a different efficiency, and that by utilizing fewer channels will save power. Additionally, unlike traditional LCD displays, OLED's don't have backlights, so darker colors draw less power.

Jeff Sharkey embarked on just that challenge and detailed his findings in his article.
Source PocketNow