Investigate colors in app/assets/stylesheets/color_modes/_dark.scss

Find out what is going on with SCSS colors defined in https://gitlab.com/gitlab-org/gitlab/-/blob/a8824fa831b9a196f32366fdbd9434dc59959225/app/assets/stylesheets/color_modes/_dark.scss and what to do with them, can they be removed? Are styles safely coming from GitLab UI for these Bootstrap SCSS variables?