Windows 10 has a Calendar app pre-installed out of the box. While Windows Vista and Windows 8 also had Calendar apps, they were not adopted by everyone. The Calendar app is useful for those who need just a basic calendar app without extra features and storing important events, appointments, holidays etc. A new update will make the app more colorful.
The stock Calendar app for Windows 10 is getting updated with more colors. If you are a Windows Insider, a newer version of the Mail and Calendar app can be installed from the Store. It comes with an extended color set than the one you have in the current version of the app available in the stable branch.
See the following screenshot.
The color palette got a color slider, which is similar to the system accent color in Settings. Now users can pick any color they want. The updated version will reach the stable branch in a few weeks. To get early access to the app, you must join the Windows Insider program and use the following link: