100% stacked bar chart with colour gradient change?

[Eamonn100]

I have a 100% stacked bar chart with 2 bars. Is there anyway to make the bar on the chart (image 1) change colour gradient (image 2) as the percentage number changes)?

 

[GraH]

Not sure if it adds more information to the chart. And I would advice against. A chart should not be a colourful picture, but a meaningful one.

But one can define a gradient fill, and add more "stops", and each stop has a defined colour. To make it easy for me, I just went with one colour and a transparency scale.