Color Coding Calendar Events
Google calendars have two color coding features. The first is color coding each calendar so that all the events on that calendar are the same. The second is to color code individual events to indicate the type of event. To color code an event:
Color coding for an event can also be added by clicking the Edit Event Details link in the pop up window and selecting the desired color while adding other details to the event.
If you use multiple calendars the color of the calendar will remain in the title bar of the event.