Colorware with Apple Products
Colorware clearly states that their customization voids Apple's warranty:


  ColorWare Inc. replaces all existing Apple Inc. warranty policies and procedures with a ColorWare Inc. warranty, the documentation for which is included with all products purchased from ColorWare Inc.


More detailed information is available at ColorWare's warranty page, where they specify that they cover "workmanship defects and non-accidental hardware failures". While this sounds similar to Apple's warranty, it would be difficult to expect similar quality of service, especially outside of the United States.