Customize (color code) folder/doc set icon in grid view of library

One of our departments has a document library with a document set for each course in their program. They'd like to color-code them by the type of course (seminar, studio or elective) in the tile view of the library. If it could also apply to the list view, that would be great, but not required.

I'm hoping this is possible using the "field customizer", but I'm not sure which field to specify in the JSON. Also, I hope that default icon in transparent, so simply specifying a background color on that div would do the trick. I'm still trying to wrap my head around the logic defining the "conditional" part of it, too, so if anyone has a good resource for understanding that, I'd appreciate the help.