Ability for providers to mark/tag patients of special interest

One of the requirements we heard from one of the implementations is to tag patients as special care patients. User should be able to get appointments for special care patients so that they can follow up with those patients. User should be able to visually differentiate appointments for special care patients. A patient will not always be a special care patient. So, a provider should be able to mark/unmark a patient as special care patient.