Highcharts Android wrapper provides its own colors implementation. As you can notice, some options are of HIColor type. You can instantiate the desired color in few ways which are described in the API documentation. In here, we will show the most complex case which is gradient usage. First, you need to create the HIGradient (you can use base constructor with default values too):

HIGradient gradient = new HIGradient(0, 0.5f, 1, 1);

Next, you should define HIStop's:

LinkedList<HIStop> stops = new LinkedList<>();
stops.add(new HIStop(0.4f, HIColor.initWithRGB(160, 160, 160)));
stops.add(new HIStop(1, HIColor.initWithRGB(60, 60, 60)));

Now you can instantiate a color thanks to those objects for, let's say, chart background:

HIChart chart = new HIChart();
chart.setBackgroundColor(HIColor.initWithLinearGradient(gradient, stops));

Original info at: the Highcharts Android wrapper GitHub repository