The CIE Yxy colour model

The CIE Yxy colour model was determined in 1931 by the Commision International de l’Eclairage to be kind of a colour triangle 1, which is often called “horse shoe” because of it’s charismatic form. The two-dimensional surface includes all perceptible colours, with the saturated colours being positioned along the outer line, the centre of the surface contained the less saturated colours, with the white point of the colour space being in the middle. Each colour has a certain point assigned to it in the coordinate system. What is problematic with this representation is the fact that distances between the colours do not correspond to the distances perceived by the eye, and that the brightness of a colour is completely disregarded.

1 The CIE Yxy colour model in two- dimensional view
1 The x-rite i1i0 photospectral meter when reading in a chart; the special feature of the newer photospectral meters is that they can automatically read in the colourmetric fields through a mechanical arm
  1. John C. Lindon (ed.), George E. Tranter (ed.), David Koppenaal (ed.): Encyclopedia of Spectroscopy and Spectrometry (San Diego: Academic Press, 2016, 3rd ed.), 328.