Setting the background to the google-charts, chart. Doesn't do anything

I draw a column chart, using the google-charts API. When i set the background to the chart it doesn't do anything.

google.setOnLoadCallback(drawChart);

  function drawChart() {
    var data = google.visualization.arrayToDataTable(<?php echo $str ?>);

    var options = {
    title: 'Business Optimization Per Predicted Conversion Rate',
    bar: {groupWidth: "70%"},
    backgroundColor: 'red',
    colors: ['purple','red'],
    fontSize:20,
    legend: { position: "none" },
    width: 900,

    };

  var chart = new google.charts.Bar(document.getElementById('chart_div_1'));
  chart.draw(data, options);
}

What's happened i wrote specific in option tag that the background need to be red?