var chart = c3.generate({
    size: { height: 240, width: 460 },
    data: {
        columns: [
            ['sample1', 30, 200, 100, 422, 150, 250],
            ['sample2', 430, 300, 500, 388, 650, 250]
        ],
      type: 'bar',
      colors: {
        sample1:    '#01B8AA',
        sample2:    '#FF9955', 
      },
      labels: {  format:  d3.format(".3") },
      groups: [  ['sample1', 'sample2']  ]
    },
    axis: {
        x: {
            label: {
                text: 'X Label',
                position: 'outer-center'
            }
        },
        y: {
            label: {
                text: 'Y Label',
                position: 'outer-top'
            }
        }
    }
});