The color of an object (in reflected or passing light) is described by various standardised parameter systems (colour spaces) with always three coordinates determined with spectral transmission values, for instance. With the aid of these coordinates the object’s colour can be unambigiously described as a colour space.
The procedure of the transmission’s measurement requires a two-sided polished and plane parallel sheet.
(Samples: plane parallel sheet, polished on both sides, 30×20 mm, thickness: 1-10 mm, tube section is possible)