As an Administrator, you can configure the card colors in the calendar for Appointments based on the Priority and Category parameters. The Priority parameter indicates the level of urgency or importance of the Appointment, such as low, medium, or high. The Category parameter indicates the type or purpose of the Appointment, such as meeting, call, or demo. You can assign different colors to different values of these parameters, so that the Appointment cards in the calendar have a visual distinction. For example, you can assign red to high priority Appointments, and blue to meeting category Appointments.

References = Calendar Card Colors Based on Appointment Priority, SAP Sales Cloud: Calendar View in Visit Planner