I want to share some excellent posts I've found about changing themes in SharePoint 2010, something even an end-user can accomplish without assistance from an administrator.
You can change themes within SharePoint, but you can also create new themes using Theme Builder (available from Microsoft Connect). In these posts, you'll find step-by-step instructions on utilizing the built-in theme tools, instructions on creating new themes using Theme Builder, and even some notes on how CSS and themes are integrated in SharePoint 2010.
The next time you want to do some relatively straightforward color changes to the site, give this collection of notes a look!
Themes Overview from TechNet
Themes on SharePoint 2010 versus 2007 from Andreas Glaser
How Themes Work in SharePoint 2010 from Sharepoint Bits
SharePoint 2010 Themes from SharePoint Branding & Design
How to Create a Custom Theme for SharePoint 2010 from Todd Baginski
SharePoint 2010 and PowerPoint Themes from the SharePoint Coffee House
Theme Builder from Microsoft Connect