title: What is this CSS property : -internal-light-dark
body: <p>I was trying to style a select element with CSS only (what a dumb idea. I know) in <strong>Edge</strong>.<br>
  I noticed while looking to the browser default (user agent stylesheet) that these lines of style were applied:</p>
  <pre class="lang-css prettyprint-override"><code>color: -internal-light-dark(black, white);
  background-color: -internal-light-dark(rgb(255, 255, 255), rgb(59, 59, 59));
  border-color: -internal-light-dark(rgb(118, 118, 118), rgb(133, 133, 133));
  </code></pre>
  <p>I tried on Chrome 87 &amp; Opera 71 and same default property is applied.
  From what I've seen, Firefox doesn't apply this.</p>
  <p>I tried to do a Google search for &quot;-internal-light-dark&quot; but found nothing. Can someone explain me what does this do?</p>