chromium/third_party/blink/web_tests/virtual/forced-high-contrast-colors/fast/css/forced-colors-mode/forced-colors-mode-13.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>
  Forced colors mode - transitions.
  Tests that color transitions work in forced colors mode.
  The only way to get transitions to work in forced colors mode is if
  forced-color-adjust is none. Otherwise, the color will always be
  overridden upon transition, and no transition will actually happen.
</title>
<link rel="help" href="https://www.w3.org/TR/css-color-adjust-1/#forced-colors-properties">
<script src="../../../../../animations/resources/animation-test-helpers.js"></script>
<style>
  #target {
    color: black;
    font-size: 50px;
    forced-color-adjust: none;
    transition: all 1s linear;
  }
  #target.final {
    color: red;
  }
</style>
<script>
  const expectedValues = [
    // [time, element-id, property, expected-value, tolerance]
    [0.5, 'target', 'color', [128, 0, 0], 64]
  ];

  function setupTest()
  {
    document.getElementById('target').className = 'final';
  }

  runTransitionTest(expectedValues, setupTest);
</script>
<span id="target">filler text</span>