Conditional shading for area between two lines

I have a web forms application in asp.net c#. I'm looking to make a chart that looks like this, that will update in real time.

I have two time series essentially, and I want to chart the difference between them green or red depending on whether the values in one of the timeseries is greater or lower.

Any suggestions for libraries/charts?

I've so far had a look at google charts and Charts.js, but haven't found something of this sort that supports conditional shading.