An 8-bpc Grayscale mode image’s pixels can only be black, white, or shades of gray.Since a Grayscale mode image has only one channel, each 8-bpc Grayscale mode image can have only 256 possible values. An 8-bpc RGB mode image has 256 possible values in each of its three color channels (red, green, and blue). It is possible for each pixel in an RGB image to be any mixture of those three colors. Therefore, each 8-bpc RGB image has 16,777,216 possible values (256 × 256 × 256).