title: Highcharts area chart with fill color relative to an overlapped line chart
body: <p>Is there a mechanism in Highcharts to have an area chart show different color based on the position relative to an overlapped line chart, such as in the following?</p>
  
  <p><a href="https://i.stack.imgur.com/pMcmh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/pMcmh.png" alt="Red and green area chart relative to line chart"></a></p>
  
  <p>The color of the area chart is relative to the line chart, with one key complication being that they may cross between two points. We're thinking we may be able to do this based on the "<a href="https://www.highcharts.com/demo/area-missing/gray" rel="nofollow noreferrer">Area with missing points</a>" example but that will require us to do the calculation of exact crossing point, which we'd rather offload if possible.</p>
  
  <p>Thanks!</p>