How to make a 9x9 RGB LED Matrix

Other Hardware LEDs and Multiplexing
5

I think you are confusing the word matrix, it has two meanings here:-

  1. the physical layout of LEDs into a grid.
  2. the way a bunch of LEDs is wired up involving multiplexing to drive them.

I am not sure what one you want. Your comment about a bunch of bits implies it is 1)
In which case look at the shiftPWM libarie and use a bunch of shift registers.