Some pages have no theme information and no favicon. In this case for coloring the only option is 'Page header background' or is 'Page header accent color'.
But when I select this, I can't use favicons in other pages.
Would be interesting having options for setting the priority like:

Page Background Color:
    [ x ] Page Theme               [ up ] [ down ]
    [ x ] Favicon     

Rewriting some things (Readme.md) seems to be necessary.

MS Edge Chromium is upcoming and Firefox as well as Chrome itself changed over the time. Some statements have to be re-checked and some statements are maybe outdated.

I's planned for end of Feb. 2020. I hope I get enough time until then to breathe and update the Readme.md file.