To resolve your issue please perform the following steps
1.Delete the existing Rainbowduino library from the Arduino IDE 1.6.8.
2.Download the Rainbowduino3.0 Library for Arduino 1.0 library from the following wiki link ([seeedstudio.com/wiki/Rainbow_Cube](http://www.seeedstudio.com/wiki/Rainbow_Cube)).
3.Install the new library into your Arduino IDE.
4.Compile the sketch.
and let us know if you have any other issues.
Note: The wiki page have two libraries.Please download the Rainbowduino3.0 Library for Arduino 1.0.