If you use Microsoft Outlook to manage your daily calendar of events and appointments, you can choose colors with predefined labels, like "Personal", "Business" or "Phone Call."

You can also create your own labels. Here's how it's done. From within your calendar, right-click an appointment or event and then click on Label. Now just click on a color-coded label on the list.

To remove the color from an appointment or event, right-click on it, click on Label, and then click on None.

To customize a label color, right-click on an appointment or event, click on Label, and then click on Edit Labels. Now pick the color you want to rename, type in your new label name, and then click OK.

Note that you can change the background color of your calendar by clicking on Tools, Options, and then clicking on the Calendar Options Button.
Now click on the down arrow that appears to the right of the Background color: box in the Calendar Options section.