chromium/third_party/blink/web_tests/external/wpt/css/css-scrollbars/scrollbar-color-dynamic-1-ref.html

<!doctype html>
<style>
  :root {
    scrollbar-color: blue green;
  }
  body {
    display: flex;
    flex-wrap: wrap;
    width: 200vw;
    height: 200vh;
  }

  .container {
    scrollbar-gutter: stable;
    flex: 0 0;
    overflow: auto;
    height: 200px;
    min-width: 200px;
    margin: 1px;
    padding: 0px;
    border: none;
    background: deepskyblue;
  }

  .content {
    height: 300px;
    width: 300px;
    background: red;
  }
</style>

<div class="container">
  <div class="content"></div>
</div>