​I have been playing with these ideas and tones, this extract is from Wikipedia:

Shibui (渋い) (adjective), shibumi (渋み) (noun), or shibusa (渋さ) (noun) are Japanese words which refer to a particular aesthetic of simple, subtle, and unobtrusive beauty.

The colors of shibusa are “muddy” colors. For example, in interior decorating and painting, gray is added to primary colors to create a silvery effect that ties the different colors together into a coordinated scheme. Depending upon how much gray is added, shibui colors range from pastels to dark. Occasionally, a patch of brighter color is added as a highlight.

The seven elements of shibusa are simplicity, implicity, modesty, silence, naturalness, everydayness, and imperfection. 

https://en.m.wikipedia.org/wiki/Shibui