While getting Quartz to work, I added my logo as an SVG to the site.

Quartz has a theme toggle, but since my logo is a single color it was not legible in the light theme. I tried changing the color to currentColor, but that didn't seem to work. Upon further investigation, I found out that there is indeed a way to get an SVG to respond to the theme of the page:

The best method for embedding dark-mode friendly SVG in HTML

<svg xmlns="http://www.w3.org/2000/svg">
  <defs>
    <style>
      svg {
        background-color: white;
        color-scheme:light dark;
      }
      @media (prefers-color-scheme:dark) {
        svg {
          background-color: black;
        }
      }
    </style>
  </defs>
</svg>

By changing the embedded css to use color instead of background-color and using currentColor instead of #ffffff as the color for strokes, I was able to modify the SVG accordingly so that it would respond to the current theme.