How to Set up and Use Color Coded Categories for Calendar (Outlook 2013)
Utilizing color coding for appointments in your calendar will allow you to see your priorities and important appointments at a glance.
Recommended minimum categories/colors:
Boulders-Dark Orange (must do tasks & projects)
Rocks–Yellow (Things you do to keep things running)
Sand–default color (quick & easy, non-crucial: ex: Sub categorizing Sent e-mails, etc.)