I added the food coloring to both toilet tanks and let set overnight.
One toilet had two streaks that came out of the rim but, never dripped into the bowl.
The other toilet appeared to be somewhat blue but, not enough for me to tell if it was serious enough to constitue the amount of in-flow that I experienced when I turned the water back on after coming home from vacation.
I also suspect that the in-flow from the meter change was a result of removing the meter and refilling it with water.
Sometime in this coming week, I'll shut off the main again and leave it off for a couple of hours and see if I experience the in-flow again.
An additional point of interest is that I do have an RO system that has a drain tube that taps into a drain line that could possibly bleed down and account for some air in the system.