To make navy blue, the colors black and blue are mixed. Blue is a primary color, and navy blue is a dark version of it, so adding black to basic blue creates the navy shade.
On a computer, colors are made by mixing red, green and blue lights. The intensity of light used for each of the three colors is represented by a number between 0 and 255. The new color is then denoted by how much intensity of each light color is used. For example, white is 255,255,255 and black is 0,0,0. Navy blue is produced with the intensity values of 0,0,128.