title: Change system css colors like ButtonFace, GrayText, Highlight, etc
body: <p>Is it possible to override the values of system CSS colors?</p>
  <p>Something like that</p>
  <pre><code>    :root {
          --ButtonFace: rgb(240, 240, 240);
          ButtonFace: rgb(240, 240, 240);
      }
  </code></pre>