Summary: At the moment, you get your unit payment warning in black which is same as your normal letters. Also, you get them too often. Instead, make it more meaningful by emphasizing it by changing its background color to read once it does become quite worrying.
Details: I believe your unit payment color changes to red on your unit status page after not paying them for 5 days so why not do the same for the report as well? Maybe if possible, you can make it something interesting by intensifying the background red color as you get near 10~11 days when your men really start to desert you. Starting at pink around day 5 to red by day 10 or so.
Benefits: Provides more meaning to the unit payment report. Also you can visually notice it better.
Possible Downsides/Exploits: Another red letter.
