JSFiddle - React, Tailwind, and code Playground

HTML

<div class = "frame"></div>

CSS

.frame {
    display: block;
    width: 100px;
    height: 100px;
    background-color: rgb(255,0,0);
}

JavaScript

var $window = $(window);
var $frame = $('.frame');

function setColor (color) {
	$frame.css('background-color', color);
}

var resizeHandler = function (event) {
    if ($(window).width() < 640) {
    	setColor('rgb(0,255,0)');
    } else {
        setColor('rgb(255,0,0)');
    }
}

$window.on('resize', resizeHandler);