There are some userChrome.css bugs in firefox 60 such the findbar (cntrl-f) text is not visible due tothe background text being white (when the difference mode is "lighter") and it doesnt automatically detect changes in theme.

it is obvoius this is no way a finished product but is this probably the smartest theme extension out currently. Overall this extension is very beautiful and im exitied to see what is added in the future.

EDIT: It appears to be a userchrome.css problem. I had a similar issue when using https://github.com/overdodactyl/ShadowFox (a very nice dark theme for firefox) and they were able to provide a fix.

I do not know how your extension works but I would reccomend contacting that developer as he is very responsive and would likely be interested in this project.

If all else fails you could open issues on stack-overflow and the mozilla help forums. Best of luck and thanks for making this extension!