I test it on my mac with the latest version SU 2019,it should work in any versions of SU,you should replace com.sketchup.SketchUp.2019 to com.sketchup.SketchUp.xxx(your SU version).
I hope you can support Mojave dark mode officially, it’s easy to implement by Apple’s guide
If you don’t like the dark mode ,you can change it back by this command:
It would break HTML dialogs that have hard-coded colors or contain background images (gif animations are not smoothly transparent) or have otherwise not been designed for having styles overridden.
By finding and editing all HTML source files (or CSS files) of buit-in dialogs and extensions one can swap the colors as well if someone finds it is a fun project.
More important are the issues in the native GUI (component description and outliner font color is hard-coded to black, VCB label and input, inspector dialog titlebars, some icons)