Here is the result
I won't go into too much detail how each part works, because I have written some information on my blog.
But you should be able to make it work with the information given on this instructable.
Step 1: Prepare RGB LED strip
you could buy led strips that have long cables, or you can just use this out of the box, it's up to you.
I am using 25 LEDs.
Step 2: Mount LED strip on TV
The sketch is how the LEDs should be mounted on the TV.
Step 3: The Connection (Arduino, Power)
You have to use external power source. I am using a 5V 2A power adapter for this.
Note: GND of the power source should be connected to the Arduino GND.
Step 4: Finally the source code
I use Processing on the computer