Although LCDs are widely used in power-consumption critical applications, they are not very energy-efficient. The largest absorber of light is the color filter. We developed a TFT-LCD with four-color subpixels: red, green, blue and white. The addition of the white subpixel greatly enhanced the light efficiency: up by 50%. The RGB-to-RGBW mapping algorithm was designed so that the hue and saturation remains unchanged from the original color. The result is a very bright display with color characteristic almost identical to RGB LCDs.