Thank you for testing. I made a change based on your opinion.
In the case of "no data" it is displayed in dark slate blue. Is this color all right? Are there other good colors?
Aside from the start of the game, this color will almost not be seen except for town building updates.

About "Staffing" case, I couldn't fix that displayed color which after the game start.
get_staffing_level_percentage() returns 100 (In other words, check_remaining_available_jobs() returns 0) even immediately after starting the game.
Buildings with all employment seem to be filled with worker like this. Therefore, it is displayed with green.

Is this a correct specification?
Also, may I ask why attractions/industries have a different text string for mail delivery success than city buildings?
To be honest with this, that is just temporary assembly... (´・ω・`)
This window already kind a chaos... but adding a mail record further increases two more rows.
I was looking for something good way and I know that it is troublesome to get out of such like a notepad.
I just placed a form that would fit the current text on the same window. In RES window show only the percentage, in others show the absolute number, so there is no special reason for that format.