I am not sure if I misunderstood the Microsoft Document (https://docs.microsoft.com/en-us/power-bi/desktop-conditional-table-formatting), which says it can be a measure. If it means the terminology "Measure" in Power BI, I don't have the luck to get this to work on a "Measure", which is preferred from my point of view, instead of creating calculated column. Did anyone succeed in using a "Measure"? My experience is it is simply not selectable.
Color formatting by field value
You can use a measure or a column that specifics a color, either using a text value or a hex code, to apply that color to the background of font color of a table or matrix visual. You can also create custom logic for a given field, and have that logic apply the desired color to the font or background.
Thanks. The dropdown menu didn't show up the measure at the begining until I draged and dropped the measure to the visual then it was able to locate it. Of course I then dropped the unwanted measure later. It's a bit strange as I don't have to perform the additonal step to find the measure.