Generally, the colour of the non-luminous objects in nature is due to absorption, diffusion and refraction of light. The colour of the optical coatings, as that of some kind of bird feathers, soap bubbles, butterfly wings, some insects, etc. is due to interference and therefore is named interference colour . This kind of colour belongs to the gonio-apparent or special-effect colours . Generally, industrial colorimetry does not deal with interference colour and the usual colorimetric instruments are inadequate to measure it. Only recently, with the new mica-pigment coatings, colorimetry is considering the measurement of the interference colour and new multiangle spectrophotometers are produced. This work is a general introduction to the ground of colorimetry and, at the end, deals with interference colours. A short overview is given of the Physiological Optics and of the Colorimetric Standards of the "Commission International de l'Eclairage" (CIE): particularly, Psychophysical Colorimetry, Psychometrical Colorimetry and Measurement Geometries are summarised. The colorimetry of gonio-apparent colours is considered. For a complete and detailed optical characterisation of interference colour the measurement of bidirectional transmittance and reflectance is needed. Particularly, basic elements for the colorimetric analysis of the interface between isotropic non-absorbing media and for thin monolayers are given.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.