The Google Calendar Android app received an update this afternoon, introducing a brand-new interface for certain steps during event creation, as well as the option to custom color-code days / your entire calendar. The new interfaces for these features are actually quite pretty, focusing on a circle-based design aesthetic that is more reminiscent of the Android 4.2 clock app in some ways.
These aren't actually huge features in terms of functionality, but they should definitely give you an idea where the Calendar app is headed in future iterations. Time zones have been simplified to be easier to determine, and you also now have more powerful options for scheduling recurring events.
The updated app
requires Android 4.2, and is rolling out in stages throughout the day. For more, check out this official Android blog post. Update: Google updated the blog post and replaced the minimum requirement of Android 4.2.1 with 4.1.