Hi :)
I don't like doing this but I will... there can be blue hole lots.
It's from having a world version without lots and using that as your base save then uninstalling, installing a world version (same world ID #) that does have lots with the old no lot save.
The game reads the lots as being there while the save reads them as not there...
Last year I was testing one world with several stages of development and seeing how they work with one save file- as if it were progression. I started with no roads, dirt roads, dirt and regular roads, then full roads. I learned how to keep a save and the families and play as if the town grew in time.
So, yeah- they would get blue lots. :(
*I can understand why it's not known much. Or I could be wrong- that happens a lot. :XD: