The Caran d’Ache colour classification system was developed scientifically on the basis of the chromatic colour circle of Wilhelm Ostwald (1853-1932). At the centre are the three primary colours: Yellow (240P), Magenta (090P) and Cyan (170P). By mixing these three colours almost any shade may be obtained.
The two inner circles comprise the CARAN d’ACHE range of pure prismatic colours, numbered with the terminate decimal 0 (zero). The shades in the outer circles are derived from pure colours darkened with black (terminate decimal 9), blended with grey (terminate decimal 2, 3, 4, 5, 6, 7 or 8) or heightened with white (terminate decimal 1).
In addition to the standard Caran d’Ache colour assortment many other shades may be obtained through blending as shown by the numbers in brackets.