title: How to define tickColor property of annotation at dygraph
body: <p>I am using Dygraph and I am setting annotations over the line chart. My problem is that I defined tickColor property for the annotation, but the annotation take the color of the trend and no the color that I am defining.</p>
  
  <p>My code:</p>
  
  <pre><code>scoreChart = new Dygraph(document.getElementById("scorechart"),
    ad,
    {
       colors: ['blue'],
       height: 200,
      });
  
  scoreChart.ready(function() {
    scoreChart.setAnnotations([{
        series: "Score",
        x: '2016/04/25 07:25:14',
        shortText: 'g120_wi',
        tickHeight: 280,
        tickColor: "red",
        attachAtBottom: true,
        tickWidth: 2
     }]);
  });
  </code></pre>
  
  <p>Result: (I hope annotation line in red as I set in tickColor property. But I want trend in blue)</p>
  
  <p><a href="https://i.stack.imgur.com/c9PO0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/c9PO0.png" alt="enter image description here"></a></p>