Hi Ivan, I am solarized only guy here. I have been using https://addons.mozilla.org/en-US/firefox/addon/solarized-light/ till now it just injects solarized colour to header(where tabs lie) of the browser. I found your extension makes colour changes to settings menu also. I liked that but I feel contrast is just not right the way solarized light should have. I guess your are using base2 in the tabs while it should be using base3 and base2 probably when hovering over it.
I guess you aren't making use of standard(or official) colour pallete. https://ethanschoonover.com/solarized/