When something is completely lacking in color, like a black-and-white photograph or a ghostly, colorless flower, it’s described as achromic.
Achromic objects stand out with their complete lack of color, like the bleached bones of an ancient skeleton or the cold, white light of a winter day. In science, this term is often used to describe tissues or cells that are completely colorless. The word achromic comes from the Greek roots a-, meaning "without," and chroma, meaning "color."