JSFiddle - React, Tailwind, and code Playground

HTML

<body>Some text</body>

CSS

body {
    height:2000px;
    background-color: #808080;
}

JavaScript

$(document).ready(function(){
    $(document).scroll(function() {
        var alpha = Math.min(0.5 + 0.4 * $(this).scrollTop() / 210, 0.9);
        var channel = Math.round(alpha * 255);
        $("body").css('background-color', 'rgb(' + channel + ',' + channel + ',' + channel + ')');
    });
});