Normally what happens if there are multiple values (numbers) for different dimension members (values) then it will check for the condition based on the calculation what have written in calculated field like below:
Here it is like for one sub-category it is green, for other it is red and so on.
In your case there are no different dimension values (members) you are showing one constant value based on the filter or without dimension.
Can you please try to put any dimension onto the rows or columns then you can see the different colors as you wrote based on your calculation.
Hope this helps.