there seems to be a lot of confusion over the efficiency of amoled vs lcd. In lcd, the power consumed directly depends upon the brightness, basically LED's provide the back-light light source and the colors you see on the screen are the representative of the kind of filters the light from the LCD had to cross to reach the surface. All lcd's are in this way passive displays. In an AMOLED display, there are three sets of actual LED's per pixel visible on screen. Each of the led making up a pixel can be individually be turned on or off, resulting in a display color, resulting in the infinite contrast and brighter colors. The current technology restricts the brightness of each of those tiny led's resulting in a lower brightness, and also the individual tiny led's brightness varies over the life of the panel. this is the biggest shortcoming for an AMOLED.

When you see a picture of light on an AMOLED screen, it is actually true that a physical light is being prepared in front of your eyes on the screen by adding the three colors in proportion. this is not an easy task and so explains why lcd's as of now display truer colors. This truly is a modern technical achievement.