Interpretation of results: The observer will see either a greyscale that is pure and free from colouring, or one which shows varying degrees of shading. If no colouring is seen, then the display is performing properly. If slight shading is seen, then the display is usable. If there is a lot of shading, then the display maybe providing false colour information. This test meets the criteria of simplicity and universality, but fails to be either quantitative or accurate. It should be used as an indication of performance of the display, but not an absolute measure. It should be noted that the identification and the degree of problem will vary according to the operator, so should not be considered as a quantitative test. C Colour Differentiation Test Diagram At the mariner's level, a testis required that reassures him that the display is functioning adequately or alternatively that servicing is required. This is provided in the Presentation Library, Part I, sections 15.4, 19.3 and 19.4. It provides test diagrams that allows the mariner to confirm that his display clearly differentiates the important colours, as well as acting as a test chart for setting the controls for night use. Note that the Colour Test Diagram must be implemented using the software specifically intended to generate this diagram, which comes with the Colours & Symbol CD, in order to ensure that the colours actually used to generate the chart display are shown on the diagram. Any other form of the Colour Test Diagram (.tif file etc) will not display the correct colours.