The proper answer is that it depends if it is classic Google Charts or Material Google Charts. If you use classic version of the Google Charts, multiple of the above suggestion work. However if you use newer Material type Google charts then you have to specify the options differently, or convert them (see google.charts.Bar.convertOptions(options)
below). On top of that in case of material charts if you specify an opacity for the whole chart, the opacity (only) won't apply for the chart area. So you need to explicitly specify color with the opacity for the chart area as well even for the same color combination.
In general: material version of Google Charts lack some of the features what the Classic has (slanted axis labels, trend lines, custom column coloring, Combo charts to name a few), and vica versa: the number formating and the dual (triple, quadruple, ...) axes are only supported with the Material version.
In case a feature is supported by both the Material chart sometimes requires different format for the options.
<body>
<div id="classic_div"></div>
<div id="material_div"></div>
</body>
JS:
google.charts.load('current', { 'packages': ['corechart', 'bar'] });
google.charts.setOnLoadCallback(drawChart);
function drawChart() {
var data = google.visualization.arrayToDataTable([
['Year', 'Sales', 'Expenses'],
['2004', 1000, 400],
['2005', 1170, 460],
['2006', 660, 1120],
['2007', 1030, 540],
['2009', 1120, 580],
['2010', 1200, 500],
['2011', 1250, 490],
]);
var options = {
width: 1000,
height: 600,
chart: {
title: 'Company Performance',
subtitle: 'Sales, Expenses, and Profit: 2014-2017'
},
// Accepts also 'rgb(255, 0, 0)' format but not rgba(255, 0, 0, 0.2),
// for that use fillOpacity versions
// Colors only the chart area, simple version
// chartArea: {
// backgroundColor: '#FF0000'
// },
// Colors only the chart area, with opacity
chartArea: {
backgroundColor: {
fill: '#FF0000',
fillOpacity: 0.1
},
},
// Colors the entire chart area, simple version
// backgroundColor: '#FF0000',
// Colors the entire chart area, with opacity
backgroundColor: {
fill: '#FF0000',
fillOpacity: 0.8
},
}
var classicChart = new google.visualization.BarChart(document.getElementById('classic_div'));
classicChart.draw(data, options);
var materialChart = new google.charts.Bar(document.getElementById('material_div'));
materialChart.draw(data, google.charts.Bar.convertOptions(options));
}
Fiddle demo: https://jsfiddle.net/csabatoth/v3h9ycd4/2/