You can create color coded categories by using the TEMPLATE feature for events.

Create an event and type the title for the event.
Click the paint can.
Choose any color you want for the event. Want a different color than what shows? Then click the plus at the top right and pick out of hundreds of colors.

Want to keep this color for future similar events?

Click on the completed event from the calendar. Click the ... at bottom right. Click add template.

This event and color will be available the next time you create an event.
Click the " template" button in the event creation screen. Your added template will show and can be used.