Customizing the SharePoint calendar is by far my most popular topic, so I thought I’d make it a little easier to find it all. Here’s what we have, for now.
Color code your SharePoint Calendar walks through how to do basic, no code, color coding in a SharePoint view.
Next, we have Customize the SharePoint Calendar Colors. This walks through how to use some basic CSS styling to change the colors of your calendar as you want.
And finally, there is a little bug that occurs when using the calendar overlay functionality. There is a little script you can apply to your page to resolve, check out Calendar Overlays: Keeping events in the same window.