The OLED is made from thousands of small LED dots , small light bulbs if you will . to create a color pixel , one of the bulbs needs to be on , and to create a white pixel three bulbs needs to be on Red , Blue , Green . So if you have a black image the bulbs are off . The LCD works by having a backlight that is constantly on and a filter of liquid crystals in front of it to filter the white light , for an LCD to display a white image , on most LCDs the crystals are into a relaxed state so it needs less power , but for black they need to be fully twisted , which needs more power , but still if you breakdown the power consumption of an LCD the backlight is biggest consumer , and the energy needed to twist the crystals is insignificant compared to that . So on an LCD it matters most what brightens level it has , and on OLED is brightens combined with color .