<!DOCTYPE html>
<html>
    <style>
        html::-webkit-scrollbar {
            background: lightblue;
            width: 50px;
            height: 50px;
        }
        html::-webkit-scrollbar-thumb {
            background: green;
        }
        html {
            background: lightblue;
            width: 500%;
            height: 500%;
            overflow: scroll;
        }
        p {
            width: 300px;
            will-change: transform;
        }
    </style>
    <p>The scrollbar tracks should be the same color with the document background color (lightblue) if the main frame supports the custom scrollbar.</p>
</html>