Hey Hui Hui, I'm assuming you're referring to the my computer controlled disco dance floor. I used a single RGB LED per tile. For my project, it was 64 tiles per board, i had 448 total LEDs. You should also pay attention to things like the brightness and field of view of the LED. Super bright but narrow field may not be optimal for you.
I have on my blog my real time thoughts on building it out over a few months along with a post on Coding4Fun. With that said, I don't know if I'd do it the same anymore. That was built before things like netduino and arduino existed.