Thoughts on best way to achieve inverted Gauge Colours

Hi All

I have searched but haven’t been able to find the answer, hopefully you can point me in the right direction…

I have setup gauges into a dashboard for various power uses in the house having recently installed solar. I am trying to get the gauge I have created for Battery Charge and Discharge to go inverted in colour. When it is being charged (positive number) it is going into my red and when negative going into the green… What am I missing?