Yes, it is possible.   No, Apex is not the only option.  

Within our software, and any other package that uses FODM to write to the GS2, you would have to publish these "background" maps as prescriptions, but you can display prescriptions as background maps w/o actually using them as a prescription.   You would assign a different rate to each each unique soil type in order to force each soil type to be displayed in a different color.  I'm not aware of a way to actually have a soil type name associated with the background map... either directly on the map or via a legend.

There is a good chance you may already be using software that can do what I described above.