gistfile1.txt

// Replace YOUR_LIGHT_COLOR_HERE with your light background.
// Replace YOUR_DARK_COLOR_HERE in two lines with your dark background.

<style>
  :root {
    --nav-background: YOUR_LIGHT_COLOR_HERE;
  }

  @media (prefers-color-scheme: dark) {
    :root:not([data-user-color-scheme]) {
      --nav-background: YOUR_DARK_COLOR_HERE;
    }
  }

  [data-user-color-scheme='dark'] {
    --nav-background: YOUR_DARK_COLOR_HERE;
  }

  .c-nav-wrap {
    background: var(--nav-background);
  }
</style>