The following is taken from the Federation of South London Photographic Societies Handbook, Section 5.b. This applies to Mono print and Mono DPI competitions.
The term “monochrome print” describes a print produced in varying densities of a single hue. Conventionally that hue would be a neutral grey, with densities from white to black. However, the neutral grey could be replaced by any single hue.
Examples of acceptable and unacceptable prints:
• A “black and white” print, uniformly printed or toned with one tone or hue, would be acceptable as a monochrome print. It would not be acceptable as a colour print in the colour print competition.
• A “black and white” print, partially toned with a single hue in addition to the base hue, is not acceptable as “monochrome”, and is regarded as a “colour” print.
• A print wholly or partially toned with two or more hues is a colour print.
• A monochrome print which has had another hue added to one element is a colour print, and is not acceptable in a monochrome competition. (e.g. coloured lips on an otherwise black and white portrait).