JSFiddle - React, Tailwind, and code Playground

HTML

<body>
<div id="foo" style="background-color: red">
    I am red
<span id="bar">
    I have no background
</span>
    
    <span id="baz" class="bg_white">
    I am white
</span>
</div>
    I am yellow
</body>

CSS

body {background-color: yellow}

.bg_white {background-color: #FFF};

JavaScript

get_bgcolor = function(obj) {
    var real = obj.css('background-color');
    var none = 'rgba(0, 0, 0, 0)';
    if (real === none) {
        return obj.parents().filter(function() {
            return $(this).css('background-color') != none
        }).first().css('background-color');
    } else {
        return real
    }
}

console.log(get_bgcolor($("#bar")));
console.log(get_bgcolor($("#baz")));
console.log(get_bgcolor($("#foo")));
console.log(get_bgcolor($("body")));