JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//ajax.googleapis.com/ajax/libs/jqueryui/1.11.1/themes/smoothness/jquery-ui.css">
<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.11.1/jquery-ui.min.js"></script>
<input>

CSS

.special span {
    color: red !important; /* should only apply to may 6 and 8 */
}

JavaScript

var disabledDates = [
    '2015-05-06',
    '2015-05-08'
];

$('input').datepicker({
    minDate: '4/30/2015',
    maxDate: '10/1/2015',
    beforeShowDay: function(date){
        var string = jQuery.datepicker.formatDate('yy-mm-dd', date);
        return [$.inArray(string, disabledDates) == -1, 'special'];
    }
});