forced-colors-mode/forced-colors-mode-54.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Forced colors mode - scrollbar-color
</title>
<link rel="help" href="https://www.w3.org/TR/css-color-adjust-1/#forced-colors-properties">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  div {
    scrollbar-color: green red;
  }
</style>
<div id="div"></div>

<script>
  test(function() {
    let value = window.getComputedStyle(document.getElementById("div")).getPropertyValue("scrollbar-color");
    assert_equals(value, "auto")
  }, "Forced colors forces scrollbar-color to auto");
</script>