Voice recognition is generally though to be outside the realm of the Arduino world, however with some help it can become a reality. Usuall this involved an expensive shield with dedicated voice-recognition microcontrollers - however if your project can be located near a PC then things become much easier. This has been demonstrated by Saurabh Vyas who created a voice-controlled RGB lamp using an Arduino and a PC running his custom VB.net application.
The PC takes care of all the voice recognition, and simply sends the resulting commands as text down the USB/serial to the Arduino. This offloads all the work to the PC, and allows the Arduino to shine in its role as the hardware controller. It's a win-win that works very well, for example the following video:
If you're looking to make your own colourful LED-based project, consider our Freetronics RGBLED: full colour module. It includes a bright RGB LED on the top of the board and a WS2801 constant-current, addressable, multi-channel LED driver on the back. This smart module can be daisy-chained, so you can connect a number of these together in a string and drive each of the module colours individually from your microcontroller. For more information and to order, visit the product page.