“An image is considered to be Monochrome only if it gives the impression of having no color (i.e. contains only shades of gray which can include pure black and pure white) OR it gives the impression of being a grayscale image that has been toned in one color across the entire image. For example by Sepia, red, gold, etc. A grayscale or multicolored image modified or giving the impression of having been modified by partial toning, multi-toning or by the inclusion of spot coloring does not meet the definition of monochrome and shall be classified as a Color Work.”
Taken from the Northwest International Exhibition of Photography competition prospectus.