Monochrome

Something which is monochromatic has a single color. In physics, the word is used more specifically to refer to a electromagnetic radiation of a single wavelength. A monochrome computer display is capable of displaying only a single color, often green or white.

The word monochromatic comes from the two Greek words mono (meaning "one"), and chroma (χρωμα, meaning "surface" or "the colour of the skin").