The RYB color format or color space builds the colors from a combination of red, yellow and blue. Each of these color values defines the intensity of the color as an integer value from 0 to 255.
As RYB is a combination of red, yellow and blue and each of these can have a value in the range of 0 to 255, it makes 16777216 possible colors. The value 255 stands for 100 percent intensity for the color value, so an RYB color of 0, 255, 0 would describe yellow.