Option to format Blanks in Calendar App color by column

Macorne

Using reports, one is only able to use drop downs for color by column. I try to use this to highlight specific items that have been tagged manually by my team (since this does not enable us to use formulas). Thus, it is a lot of hard work to create a separate manual tag for blank items, in order to control the color those show up as on the calendar.

I would like the ability to control the color of blank items on the color by column option for the calendar app.