If you aren't comfortable using CSS for advanced customization of Events, you can specify HTML directly in the Event Title field.
For example, if you wanted to make the title text of a particular event display in red, you could use this HTML:
Or perhaps you want red and bold:
How's about a bigger font?
You can use almost any HTML in the Title field. Be careful and make sure to Preview your Event before saving it. Otherwise, if your HTML has problems your calendar may not be displayed correctly.
Enter this text into your calendar Title or Footer field under Options->General:
The various CSS hooks localendar exposes are documented on this page.