title: highchart-ng update color on bar
body: <p>I want to change color on a bar dynamically in a column chart  using highchart-ng.
  I see that the $watch function in highchart-ng is triggered each time the $interval is changing the color, but no update of the color is made eventhough the chart.redraw() is called each time.</p>
  
  <p>However, if I at the same time add a new bar dynamically(see outcommented code in jsfiddle) the bar changes color.</p>
  
  <p>jsfiddle.net/rick822/k7pbwch4/</p>