Computers don't have colors inside them, of course. Instead, colors are represented inside the computer with three numbers specifying the amount of each primary color in a given color: {Red, Green, Blue}. The short way to say it is the 'RGB' representation.

In some representations, the value range for each primary color is 0-255. So {0,0,0} is black, {255,255,255} is white, and {255,0,0} is red.

An image is represented as a table of RGB values:

RGB	RGB	RGB	RGB	RGB
RGB	RGB	RGB	RGB	RGB
RGB	RGB	RGB	RGB	RGB
RGB	RGB	RGB	RGB	RGB
RGB	RGB	RGB	RGB	RGB