The parts of the human eye that are responsible for color perception are called cone cells or photoreceptors. RGB is called an additive color system because the combinations of red, green, and blue light create the colors that we perceive by stimulating the different types of cone cells simultaneously. RGB color is best suited for on-screen applications, such as graphic design. Each color channel is expressed from 0 (least saturated) to 255 (most saturated). This means that 16,777,216 different colors can be represented in the RGB color space.