Monochrome

[Sarah]

When an image is in black and white or it quite likely to be grey scale

[Kai]

The word monochrome literally means one color. Therefore, a monochrome image only includes one color, but may contain many shades. In computing, monochrome typically refers to a two-tone image, rather than one with several shades of a single color. For example, a monochrome monitor uses one color for the background and another to display text or images on the screen.
Before color monitors became standard, most computers had monochrome displays. These displays often had a black background with green text, though some displayed text in other colors, such as red or orange. While this may seem like a rudimentary way to display text, it was sufficient for typing documents, since computers still offered more text editing capabilities that a typewriter. Even after color monitors became the norm in the 1980s, monochrome displays were still used for several years as computer terminals.
Today, monochrome computer monitors are rare. By the time LCD displays replaced CRTs monitors in the early 2000s, monochrome screens had already been obsolete for several years. Now, even basic terminal displays support a wide range of colors. While you might not see monochrome monitors today, monochrome displays can still be found in other electronics, such as watches, timers, and digital clocks.
NOTE: Monochrome is not the same thing as grayscale. A grayscale image is a type of monochrome image that only contains shades of gray. Additionally, monochrome and black-and-white are two different things. The phrase black-and-white may refer to a monochrome image that only includes the colors black and white or a grayscale image with multiple shades of gray.

[Hina Muqadas]

Literally one color. A monochrome display is commonly known as a black and white or grayscale display. In mobile phones such black-and-white displays often utilize a colored backlight such as green, blue or orange.
Monochrome displays are no longer used for primary displays in mobile phones, but some are still used as external secondary screens.

[Becky]

A photograph or picture developed or executed in black and white or in varying tones of only one color.

[Britney]

Monochrome (also known as Checkmate or Checkmating) is the femslash/yuri/wlw ship between [Weiss Schnee] and [Blake Belladonna] from the American anime-style web series RWBY.
Weiss Schnee and Blake Belladonna are teammates and make up the W and B of Team RWBY, respectively. Weiss was the heir to the Schnee Dust Company and initially had distrust of the White Fang and of the [Faunus] (one of two races in the world of RWBY that is distinguishable in that they possess the traits of animals). Due to this, she initially runs into conflict with Blake, who grew up in the White Fang and is a Faunus. Over time, they learn to trust each other and now consider each other like family.

[Sommer]

using only black, white, and grey, or using only one colour: