I appreciate your help, but I think it's clear that the status icons on the left are not very intuitive.
They seemed quite obvious to me, but then I played on a large map with a lot of cities.
That makes the blue dots quite obvious - that capital has a lot, the next city half as many, that new village has none.
As I tend to keep all my cities building something all the time, the idle one really sticks out - which again makes the connection to the yellow border obvious.
For the red dots just notice how they change when you move your main stack into that new village threatened by monsters.
And finally there's the meta hint: the game programmers thought some info important enough to put it into the list - what could it be? Or, reversing the question, what would I want to know at a glance about my cities? Could one of the graphics tell me that?