Click on cell D14
Click on Conditional Formatting menu and choose Manage Rules.
![Conditional Formatting rules for calendar](https://indzara.com/wp-content/uploads/2017/02/Conditional-Formatting-rules-for-calendar.jpg)
Click on any rule and select Edit Rule.
![Change color for any rule](https://indzara.com/wp-content/uploads/2017/02/Change-color-for-any-rule.jpg)
Click on Format to change color. In the image above, I have chosen the rule that applies purple color to Holidays.
After changing colors, click OK in the dialog boxes and apply changes.