If you're handy with CSS and know how to use your browser's source inspector tools to figure out which elements need to be overriden, then install the Stylus browser addon and start tweaking your own CSS override stylesheet for SW to your liking, for light or dark mode
I don't change the color scheme, but you can use my Stylus stylesheet as a template:
https://gist.github.com/venteto/26b95cde784c4d93a885a43672dc78f0
the color palette isn't something I really pay attention to, my mind is on other things, the color scheme is fairly trivial compared to other aspects