I am constructing a 5x5 LED grid that has an RGB LED under a plastic cover, and a piezo sensor that changes the RGB LED to one of 8 colors when pressed.
So as far as I can tell I need 75 outputs for the RGB LEDs, plus 1 more to power everything that can be daisy chained between the 25 RGB LEDs. I will also need another 25 inputs for the piezo sensors and 1 ground that can be daisy chained together.
The Arduino has nowhere near enough I/O pins on it but I have heard of a thing called multiplexing. However, I am not sure if you can run RGB leds with multiplexing.
If this helps at all I am using a led strip that I can cut into 3 LED sections to put under each square.
I hope I was not to vague with my question, thanks for your help.