In QGIS (using ver. 3.16) , you can use the categorized symbology renderer for polygons to assign a certain color to polygons with the same attribute value. There is also the Topological coloring algorithm to assign a value to each polygon in such a way that no adjacent polygons share the same color. Both works perfect.
However, I want to have a "nested" coloring of polygons - in the same style as this map here: https://i.stack.imgur.com/rgiqh.jpg
So there should be a main color for the first order territorial units (say: blue, green, red), whereas all subordinated second order terrritorial units should be assigned a variation of this basic color (like: dark, light... blue, green, red).
A workaround would be to treat each first order territorial unit separately as an own layer and apply to each a categorized styling, using diffent color-ramps: blues, greens, reds. But this is quite cumbersome.
Is there a better way to achieve this?