RGB stands for RED, GREEN and BLUE respectively, the so-called three primary colors of light, and then these three are combined into different colors. Video game hardware that has appeared in recent years often advertises a color development capability of 16.77 million colors. The calculation method is that the three colors of red, green, and blue can be set for 256 stages of light and dark. 256 = 16777216 colors. There are two common forms in RGB input terminals: 21PIN and 15PIN RGB terminals. There is no difference between the two, the difference is that the former only has Composite Sync (synthetic synchronization signal), while 15PIN still subdivides Composite Sync into H-Sync (horizontal synchronization signal) and V-Sync (vertical synchronization signal). The 15PIN RGB terminal is already a standard specification for general computer screens, as for home TVs, it is rarely seen with RGB input.