Individual Background Color for Classes per css class suffix

Hi,
actually I use categories for class Background color in the time schedule. is there a way to add a css class suffix to the individual classes?
so that the class item style is" background color by address" ?
background to this. I have five classrooms which are now created as addresses. for example, if the course is in room 1 the background colour should be blue. in room 2 green, in room 3 yellow, and so on. The whole thing is independent of the catergories, which I want to continue to use as before. It would be enough for me to have a css suffix for the background colour, e.g. cr1 (classroom1) cr2, cr3, etc.

Thank you so much. But it dosen't appear on the front end also after clearing cache.
Maybe the problem ist view 'month' instead of 'week' ?

Please recheck it.
Regards