JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://arshaw.com/js/fullcalendar-1.5.3/fullcalendar/fullcalendar.css">
<script src="http://www.arshaw.com/js/fullcalendar-1.5.3/fullcalendar/fullcalendar.min.js"></script>
<div style="border:solid 2px red;">
        <div id='calendar'></div>
</div>

CSS

.places-green {
}

.places-orange {
    border-color: #E08E1B !important;
    background-color: #E08E1B !important;
    color: #FFFFFF !important;
}

.places-red {
    border-color: #E01B35 !important;
    background-color: #E01B35 !important;
    color: #FFFFFF !important;
}

JavaScript

$(document).ready(function() {

    var date = new Date();
    var d = date.getDate();
    var m = date.getMonth();
    var y = date.getFullYear();

    var events_array = [
        {
        title: 'Cal Give Back Test With Space',
        start: new Date(2017, 7, 20),
        url: 'opportunityDetailUsr.php?id=4&gid=153',
        places: 5},
    {
        title: 'Cal Give Back Test With Space',
        start: new Date(2017, 7, 21),
        url: 'opportunityDetailUsr.php?id=4&gid=153',
        places: 0}
    ];

    $('#calendar').fullCalendar({
        header: {
            left: 'prev,next today',
            center: 'title',
            right: 'month,agendaWeek,agendaDay'
        },
        editable: true,
        events: events_array,
        eventRender: function(event, element, view) {
            if(event.places>0 && event.places<=5) {
                element.find('.fc-event-skin').addClass('places-orange');
            }
            else if(event.places===0) {
                element.find('.fc-event-skin').addClass('places-red');
            }
        }
    });
});