user_preferences-member-manual.html

<!DOCTYPE html>
<title>Test that user_preferences member is supported</title>
<link rel="manifest" href="resources/user_preferences-member.webmanifest" />
<script src="resources/user_preferences-member-manual.js"></script>
<h1>Testing support for user_preferences member</h1>
<ol>
  <li>Install this site as a PWA</li>
  <li>Enable the OS dark mode setting</li>
  <li>To pass, the theme_color must be green. This can be observed by looking
    at the top of the window. On failure, this will be red.
  </li>
</ol>

chromium/third_party/blink/web_tests/external/wpt/appmanifest/user_preferences-member/user_preferences-member-manual.html