Redmine

Many apps and mobile devices offer Dark Mode as a standard per-user setting.

Would love to have this feature on my website

found this plugin: https://github.com/fraoustin/redmine_dark

and this as well: https://9to5tutorial.com/use-dark-mode-in-redmine
https://darkmodejs.learn.uno/
https://github.com/onozaty/redmine-view-customize

not perfect, but makes the site dark

Is it possible to create a completely color-inverted skin based on the default one?

Would anyone among the redmine developer community be interested in implementing this? If the amount of effort is rasonable, I might be willing to fund the related development. The important part is that it's not a separate global per-site theme, but a per-user setting. Or alternatively even simply automatically use dark mode if the OS/browser request it.