Google Chart在轴标题中显示多种颜色

<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>

google.charts.load('current', { 'packages': ['corechart'] });
google.charts.setOnLoadCallback(drawChart);

function drawChart() {
  var data = google.visualization.arrayToDataTable([
    ['Year', 'Sales', { role: 'style' }],
    ['2018', 1000, 'color: blue'],
    ['2019', 1500, 'color: green'],
    ['2020', 2000, 'color: red']
  ]);

  var options = {
    title: 'Sales by Year',
    hAxis: { title: 'Year', titleTextStyle: { color: '#333' } },
    vAxis: { minValue: 0 },
    legend: 'none'
  };

  var chart = new google.visualization.ColumnChart(document.getElementById('chart_div'));
  chart.draw(data, options);
}

<div id="chart_div"></div>