change color of last months date react big calender code example

Example: react big calendar event color

eventStyleGetter: function(event, start, end, isSelected) {
    console.log(event);
    var backgroundColor = '#' + event.hexColor;
    var style = {
        backgroundColor: backgroundColor,
        borderRadius: '0px',
        opacity: 0.8,
        color: 'black',
        border: '0px',
        display: 'block'
    };
    return {
        style: style
    };
},

render: function () {

    return (
        <Layout active="plan" title="Planning">
            <div className="content-app fixed-header">
                <div className="app-body">
                    <div className="box">
                        <BigCalendar
                            events={this.events}
                            defaultDate={new Date()}
                            defaultView='week'
                            views={[]}
                            onSelectSlot={(this.slotSelected)}
                            onSelectEvent={(this.eventSelected)}
                            eventPropGetter={(this.eventStyleGetter)}
                            />
                    </div>
                </div>
            </div>
        </Layout>
    );
}