Kai:
We don't know how big of matrix that Mr Cousin wants, but I suspect that with the multiple colore he mentiones he is looking at a rather large array to do graphic type displays. Most often the multiplex scheme is the only efficient method. I go along with Daniael on the use of high current driver like the trasistors type chips. I have made multiplexed displays in the past where I ran a 1/16 duty cycle and then boosted the LED current to about 10X the normal levels. If you run fast enough there will not be any apparent flicker unless the display moves rapidly across your field of vision.
Michael Karas