Note: Folders Factory is no longer under development and the developer provides no support for it.
With Folders Factory, you can easily change their colour, add pictures, include text or even make them look like "embossed" system folders.
Doing this will improve your performance and your system's appearance. You'll no longer have to read folder names as you can now easily identify the one you need.
The application is very user-friendly. All you have to do is: drag the image you want into the application's window, configure the way it looks, and then drag the folder you want to modify there too. Done.