sao/www/bower_components/c3/docs/js/samples/style_region.js

var chart = c3.generate({
    data: {
        columns: [
            ['sample', 30, 200, 100, 400, 150, 250]
        ]
    },
    regions: [
        {start:0, end:1},
        {start:2, end:4, class:'foo'}
    ]
});