hexo-theme-next/source/css/_colors.styl

:root {
  --body-bg-color: $body-bg-color;
  --content-bg-color: $content-bg-color;
  --card-bg-color: $card-bg-color;
  --text-color: $text-color;
  --selection-bg: $selection-bg;
  --selection-color: $selection-color;
  --blockquote-color: $blockquote-color;
  --link-color: $link-color;
  --link-hover-color: $link-hover-color;
  --brand-color: $brand-color;
  --brand-hover-color: $brand-hover-color;
  --table-row-odd-bg-color: $table-row-odd-bg-color;
  --table-row-hover-bg-color: $table-row-hover-bg-color;
  --menu-item-bg-color: $menu-item-bg-color;
  --theme-color: $theme-color;

  --btn-default-bg: $btn-default-bg;
  --btn-default-color: $btn-default-color;
  --btn-default-border-color: $btn-default-border-color;
  --btn-default-hover-bg: $btn-default-hover-bg;
  --btn-default-hover-color: $btn-default-hover-color;
  --btn-default-hover-border-color: $btn-default-hover-border-color;

  --highlight-background: $highlight-background;
  --highlight-foreground: $highlight-foreground;
  --highlight-gutter-background: $highlight-gutter-background;
  --highlight-gutter-foreground: $highlight-gutter-foreground;

  color-scheme: light;
}

if (hexo-config('darkmode')) {
  @media (prefers-color-scheme: dark) {
    :root {
      --body-bg-color: $body-bg-color-dark;
      --content-bg-color: $content-bg-color-dark;
      --card-bg-color: $card-bg-color-dark;
      --text-color: $text-color-dark;
      --selection-bg: $selection-bg-dark;
      --selection-color: $selection-color-dark;
      --blockquote-color: $blockquote-color-dark;
      --link-color: $link-color-dark;
      --link-hover-color: $link-hover-color-dark;
      --brand-color: $brand-color-dark;
      --brand-hover-color: $brand-hover-color-dark;
      --table-row-odd-bg-color: $table-row-odd-bg-color-dark;
      --table-row-hover-bg-color: $table-row-hover-bg-color-dark;
      --menu-item-bg-color: $menu-item-bg-color-dark;
      --theme-color: $theme-color-dark;

      --btn-default-bg: $btn-default-bg-dark;
      --btn-default-color: $btn-default-color-dark;
      --btn-default-border-color: $btn-default-border-color-dark;
      --btn-default-hover-bg: $btn-default-hover-bg-dark;
      --btn-default-hover-color: $btn-default-hover-color-dark;
      --btn-default-hover-border-color: $btn-default-hover-border-color-dark;

      --highlight-background: $highlight-background-dark;
      --highlight-foreground: $highlight-foreground-dark;
      --highlight-gutter-background: $highlight-gutter-background-dark;
      --highlight-gutter-foreground: $highlight-gutter-foreground-dark;

      color-scheme: dark;
    }

    img {
      opacity: .75;

      &:hover {
        opacity: .9;
      }
    }

    iframe {
      color-scheme: light;
    }
  }
}

if (hexo-config('lightdark.enable')) {
  +light-dark-block() {
    :root {
      --body-bg-color: light-dark($body-bg-color, $body-bg-color-dark);
      --content-bg-color: light-dark($content-bg-color, $content-bg-color-dark);
      --card-bg-color: light-dark($card-bg-color, $card-bg-color-dark);
      --text-color: light-dark($text-color, $text-color-dark);
      --selection-bg: light-dark($selection-bg, $selection-bg-dark);
      --selection-color: light-dark($selection-color, $selection-color-dark);
      --blockquote-color: light-dark($blockquote-color, $blockquote-color-dark);
      --link-color: light-dark($link-color, $link-color-dark);
      --link-hover-color: light-dark($link-hover-color, $link-hover-color-dark);
      --brand-color: light-dark($brand-color, $brand-color-dark);
      --brand-hover-color: light-dark($brand-hover-color, $brand-hover-color-dark);
      --table-row-odd-bg-color: light-dark($table-row-odd-bg-color, $table-row-odd-bg-color-dark);
      --table-row-hover-bg-color: light-dark($table-row-hover-bg-color, $table-row-hover-bg-color-dark);
      --menu-item-bg-color: light-dark($menu-item-bg-color, $menu-item-bg-color-dark);
      --theme-color: light-dark($theme-color, $theme-color-dark);

      --btn-default-bg: light-dark($btn-default-bg, $btn-default-bg-dark);
      --btn-default-color: light-dark($btn-default-color, $btn-default-color-dark);
      --btn-default-border-color: light-dark($btn-default-border-color, $btn-default-border-color-dark);
      --btn-default-hover-bg: light-dark($btn-default-hover-bg, $btn-default-hover-bg-dark);
      --btn-default-hover-color: light-dark($btn-default-hover-color, $btn-default-hover-color-dark);
      --btn-default-hover-border-color: light-dark($btn-default-hover-border-color, $btn-default-hover-border-color-dark);

      color-scheme: light dark;

      img {
        opacity: light-dark(1, .75);

        &:hover {
          opacity: light-dark(1, .9);
        }
      }

      iframe {
        color-scheme: light;
      }
    }
  }
}