JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/c3/0.4.10/c3.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/c3/0.4.10/c3.js"></script>
<div id="chart"></div>

CSS

.over {
    fill: red;
}

JavaScript

(function() {
    var chart = c3.generate({
        bindto: '#chart',
        data: {
            columns: [
                ['data', 1, 3, 2, 4, 3]
            ]
        }
    });

    setTimeout(function() {
        chart.regions([
            { axis: 'x', start: 1, end: 2, class: 'over' }
        ]);
    }, 1000);
    
    setTimeout(function() {
        chart.regions([
            { axis: 'x', start: 3, end: 4, class: 'over' }
        ]);
    }, 2000);
})();