If you want to customize Google Chrome, you can now download alternative theme files. Go to Chromespot’s themes board and look for something you like; maybe the Firefox theme, a green one, or the simple gray theme called Blurk. Each theme contains a file called “default.dll”, which you need to copy over your original default.dll. Note: Make sure to backup of the original first.
Here’s the path you need to replace the file:
In Vista: C:\Users\[your user name]\AppData\Local\Google\Chrome\Application\[current version]\Themes\
In Windows XP: C:\Documents and Settings\User\Local Settings\Application Data\Google\Chrome\Application[current version]\Themes\
Source:→ Google Blogoscoped