RGB
Screen colour made by mixing red, green and blue light, each from 0 to 255.
See it in Image glitch. Open Channel shift and move the red, green and blue offsets apart.
In plain words
Every colour on a screen is a mix of red, green and blue light. Each of the three is a number from 0, which is off, to 255, which is full. All three at 255 make white, and all three at 0 make black. Red and green together make yellow, because light adds up, unlike paint. The three numbers are called channels, and a picture stores them for every pixel.