A CDE Definition

Also called "mono." Refers to display screens that use one foreground and one background color; for example, black on white, white on black or green on black. The first terminals connected to mainframes and minicomputers were monochrome, and monochrome screens were widely used on early personal computers.

Monochrome Vs. Grayscale
Quite often, a non-color monitor is called monochrome; however, if it displays shades of the single color, then it is a grayscale monitor. See pixel and color depth.