title: Set bubble transparency in Highcharts?
body: <p>Is there a way to influence the transparency of the bubbles in Highcharts bubble charts?
  I was looking for a configuration comparable to area fillColor, but didn't find one.</p>
  
  <p>I tried using  rgba colors for the series, like so:</p>
  
  <pre><code>       series: [{
          color: "rgba(255,0,0,0.5)",
          data: [ 
  </code></pre>
  
  <p>but that only made the border semi transparent.</p>
  
  <p>Edit: 
  I just tried to use marker fillColor:</p>
  
  <pre><code>series: [{
          color: "rgba(255,0,0,1)",
          marker: {
              fillColor: "rgba(255,0,0,0.1)"
          },
  </code></pre>
  
  <p>but that doesn't influence the transparency</p>