Range of blue tones

Three colour charts demonstrating the range of the colour blue as it moves from white to black.

Figures 1, 2 and 3 from Michel Eugene Chevreul’s Expose d'un moyen de definier et de nommer les coleurs d'apres unem ethode precise et experimentale… [Presenting a way to define and name the colours according to a precise and experimental method…]

Written in the description [as translated to English]:
‘Fig 1. Example of the graduation of a colour. We go from white to black.
Fig 2. This is figure 1, divided into 22 equal superficial parts.
Fig 3. This is figure 2, except the colour that is graduated in a continuous manner in figure 2 is now distributed in a uniform manner on each superficial part.’

Figure 3 demonstrates the Chevreul’s method of definition: to represent colours in individual ‘parts’ that accommodate their variance in tone and brightness. His colour system was one of the first to do this.