> only changes the colors for syntax highlighting -- which is now slightly broken in the dark mode

might be of use:

  @supports (color-scheme: dark light) {
      @media screen and (prefers-color-scheme: dark) {
          code { ... }
      }
  }

My current solution is to switch the syntax highlighting to monochrome which should work fine for both modes. I love the colorful syntax highlighting, though. So maybe I will revisit this later to find out if I can do something along the lines of what you suggest.