Colour cell background in a pivot table based on date comparison

[s_mapper319]

Hello!

I am trying to dynamically change the background colour of specific cells in a pivot table based on a date comparison. If the date in the pivot table matches a flagged date from another table (see "Varning" table in the bottom right corner of the image below), I want the cells in the pivot table to be red.

I have tried using the background colour expression under my measurement value, and it works when I try a dummy expression like "if(value > 1000, blue(), red())", but when I try to compare dates, it doesn't work "if(pivot.date = flagged.date, red(), green())".

Any help greatly appreciated!