I know this thread has been going on for years, and some patterns seem to have formed in the various dots on the springs. But one of the first things that came to mind, was that the dots are just assembly checks. One guy on the line installs his part, and puts a dot on a certain coil. The next guy installs his part, and then adds a dot. When the car reaches the end of the suspension installation, they check that all the dots are present, and the car goes on to be completed. I would assume the suspension is such a safety concern that insuring everything is installed, and torqued would be a priority.
This could explain different dots for different versions, separate assembly lines and different workers. Each worker may have a different color. And it could explain cars that are the same model having different dots, worker A is sick one day, worker B takes his place and puts his different dot in the same place worker A would have.
Just an idea.