Describes the method for determining the colour co-ordinates of paint films. The method is only application to paint films that appear to be uniformly of one colour (monochromatic), when examined with normal vision. Paint films that do not completely hide a non-transparent substrate may be measured by using this procedure. All the other paint films are outside the scope. The principle consists in measurement of the spectral photometric characteristics (spectral reflectances or spectral reflectance factors) with a spectrophotometer or measurement of the tristimulus values with a tristimulus colorimeter. Calculation of the chromaticity co-ordinates by a table.