Ok so I'm no expert on ePaper displays, but I do have a nice base understanding​ of what occurs. All ePaper displays consist of small little balls. Each balls could be be colored half black and half white or half of them could be colored fully white and the other half fully black. For this explanation I will focus on the type of display where each ball has two colors, however, both perform the same function. These balls are then held in a cube that is filled with a water like solution. These cubes make up each "pixel" of the display. Depending on the polarity of voltage applied to the pixel, the balls will either show their white or black side. Using this method, the designers now have a matrix of individually controlled pixels to drive.

Well that's all good, but it only applies to black and white. How does color work? Well, color actually uses the exact same setup, but on top of the pixels is an rgb filter, that switches colors in order to show different hues on the display.

Pebble designers used ePaper because after the balls show black or white, no more battery power is needed to keep them in their positions. This contributes to the long battery life of pebbles. The color displays of pebbles requires a bit more battery power to power the rgb filter, but it's still vastly better than an LCD.