Office 365 (Outlook 2013 | 2010) - Change calendar color
Outlook’s Calendar feature offers a total of 15 soft colors that you can apply to your calender. This may particularly come useful in situations where you are viewing multiple calendars side-by-side, and want to quickly make changes to the calendars. Not only does it allow you to change the color of the calendar from within the calendar window, it also lets you choose your favorite color from the main navigation bar. When you change the color of the calendar, it also changes the hover and selection color in navigation bar. The selection color helps a user in identifying the type of calender.
Since it may become quite confusing if all calendars are of the same color, we recommend choosing different colors for your calendar. Nevertheless, if you deal with more than 9 (Outlook 2013) or 15 (Outlook 2010) calendars, you can choose to assign the same color to a group of calendars that belong to a specific category. In order to change calendar’s color, right-click on calendar area, from Color menu, select the required color.
Note: Images below are from Outlook 2010.
This will immediately change the color of your calendar. Similarly, you can apply different color to your calendar.
As stated earlier, you can also change the color of the calender from the main navigation bar. All you need is to select the calendar, right-click it, and choose the color from Color menu.