chromium/third_party/blink/web_tests/fast/forms/color-scheme/select/select-inpage-appearance-basic.html

<!DOCTYPE html>
<meta name="color-scheme" content="light dark">
<script src="../../../../resources/run-after-layout-and-paint.js"></script>
<script src="../../resources/common.js"></script>
<body>

<!-- no style for reference -->
<select><option>unstyled</option></select> <br>

<!-- rtl -->
<select dir="rtl"><option>right-to-left</option></select> <br>

<!-- focused -->
<select id="focusTarget"><option>focused</option></select> <br>

<!-- hovered -->
<select id="hoverTarget"><option>hovered</option></select> <br>

<!-- disabled -->
<select disabled><option>disabled</option></select> <br>

<!-- colored text -->
<select style="color:darkturquoise"><option>turquoise text</option></select> <br>

<!-- border -->
<select style="border: 3px solid lime;"><option>thick lime border</option></select>
<select style="border-radius: 6px;"><option>border-radius: 6px</option></select>
<select style="border:none;"><option>border:none</option></select><br>

<!-- background -->
<select style="background: linear-gradient(to bottom, #dea 0%,#9c7 44%,#494 100%);"><option>gradient background</option></select> <br>

<!-- shadow -->
<select style="box-shadow: 4px 4px 10px rgba(255,0,0,0.5), inset 4px 4px 4px rgba(0,255,0,0.5);"><option>box-shadow</option></select> <br>

<!-- arrow clipped -->
<select style="width: 24px; height: 5px;"><option>size: 8px</option></select>
<select style="width: 8px; height: 8px;"><option>size: 8px</option></select> <br>

<!-- size -->
<select style="width: 16px; height: 16px;"><option>size: 16px</option></select>
<select style="width: 24px; height: 24px;"><option>size: 24px</option></select>
<select style="width: 26px; height: 20px;"><option>width: 26px; height: 20px</option></select>
<select style="width: 60px; height: 60px;"><option>size: 60px</option></select> <br>

<!-- zoom -->
<select style="zoom: 1.5;"><option>zoom: 1.5</option></select>
<select style="zoom: 3;"><option>zoom: 3</option></select> <br>

<script>

runAfterLayoutAndPaint(function() {
  let focusTarget = document.getElementById('focusTarget');
  focusTarget.focus();

  let hoverTarget = document.getElementById('hoverTarget');
  hoverOverElement(hoverTarget);
}, true);

</script>
</body>