title: Change colours of particular bars in a bar chart
body: <p>I've been creating some bar-charts and I was wondering is it possible to colour bars on a chart depending on whether they lie above or below the x-axis?</p>
  
  <p>For clarification, this is the type of bar-chart I mean:</p>
  
  <p><img src="https://i.stack.imgur.com/SfmeD.png" alt="enter image description here"></p>
  
  <p>Ideally I would like to be able to colour the bars above a separate colour to those below so the graph looks more appealing, I've been searching but I can't find any method of doing this, can anyone help?</p>
  
  <p>Thanks in advance. :)</p>