The functional use of colour on visual display units: Air traffic control displays

Where full-colour monitors are used for information displays, the use of colour must take into account ergonomic, perceptual, cognitive and aesthetic factors. Air traffic control displays are a safety-critical application where it is essential that colour should not be used inappropriately. This paper describes an approach to the use of colour for  displays whereby the objects on the display are assigned to a series of conceptual layers which are in turn represented as visual layers. Background map features are shown as opaque infills, overlaid with transparent infills for overlapping areas; alphanumeric labels in the foreground are shown in black, each with an attached infill to ensure good legibility and effective colour coding. Colour palettes are provided for each layer so that the display designer has flexibility but can be confident that the display will be free of colour illusions and ambiguities. The resulting displays can be used in normal office lighting. (The work was undertaken for the Chief Scientist's Division of the National Air Traffic Services, part of the UK Civil Aviation Authority.)