Can a feature not be added to allow the user to change the colour of the text slots. This will allow the user to predefine slots for certain types of treatment. If you are able to do appointments at the moment it should be pretty straight forward to add the feature to allow users to colour code text slots.
The terminology that you're using when asking about this feature makes me think you may be in the wrong product section of the forum, as well as that your email is a .UK based email.
can you confirm if your office uses the CS PracticeWorks software of the CS R4+ software?