Color: red and green led together produced as a pixel display called color screen or color screen; the red, green and blue LED tube together as a pixel display called the tri-color screen or full color . Pixel: make indoor LED screen pixel size is usually 2-10 mm, often used to produce several different color LED die into one package. Outdoor LED screen pixel size, mostly 12-26 mm, each pixel is composed of several kinds monochromatic LED, which is common product of say pixel tube. Color pixel tube is generally composed of three Red 2 green, three-color pixel tube with 2 red 1 green 1 blue components. Whether with LED production monochrome, color or tri-color screen, to display the image needs to constitute emission brightness of each LED pixel must be able to adjust the fine degree of adjustment that the gray levels. The higher the level grayscale image displayed more delicate, the color is richer, the corresponding display control system is also more complex. General 256 gray-scale images, color transition has been very soft, and the 16-level grayscale color images, color transition boundary is very obvious. Therefore, the current color LED screen are required to make 256 gray.