Refers to a single-color or black-and-white visual style, often in photography, art, or design. The more common everyday term is モノクロ.
この写真はモノクロームで撮影されている。
This photo was taken in monochrome.
モノクロ is the everyday, casual abbreviation, while モノクローム is the fuller, slightly more formal or technical term for the same black-and-white concept.
From English 'monochrome'.