Monochrome

In physics, monochromatic light refers to electromagnetic radiation that contains a narrow band of wavelengths, which is a distinct concept.

Of an image, the term monochrome is usually taken to mean the same as black and white or, more likely, grayscale, but may also be used to refer to other combinations containing only tones of a single color, such as green-and-white or green-and-red.

In digital photography, monochrome is the capture of only shades of black by the sensor, or by post-processing a color image to present only the perceived brightness by combining the values of multiple channels (usually red, blue, and green).

Monochromatic color schemes provide opportunities in art and visual communications design as they allow for a greater range of contrasting tones that can be used to attract attention, create focus and support legibility.

That means according to science the true monochromatic images can be strictly created only of shades of one color fading to black.

Black-and-white monochrome: the Eiffel Tower during the 1889 Exposition Universelle
Color monochrome: night-vision devices usually produce monochrome images, typically in shades of green.
A photograph of a macaw rendered with a monochrome palette of a limited number of shades
A Philips branded digital audio player with a monochrome display and green backlight, common on older devices including mobile phones and handheld game systems
Example of a monochromatic color scheme
Monochromatic color gradient on color wheel