Butterfly Chart Colour Measure by Expression

[william_goodwin]

 Hi, 

I am new to Qlik sense and I am having problems colouring the bars in my butterfly chart by an expression. I have modified the attached image of a butterfly chart from Google. I have the butterfly chart and it looks good but I want to colour the bars for one measure using an expression. I have edited the example below to show what I want to do.  The green I have added represents a % of the 'Cost' measure. 

Hopefully, there is enough detail above, if not I can add more information. Unfortunately, I cannot share the data for my dashboard.