do you think i will need any external driver if I plan to use 3 TLC5940s? These will still control 16 rgb leds.. i am planning on using 15ma i guess for longer lifeDriver for what?
You shouldn't need one when used with the TLC5940.
Keep in mind that the way it works is different the 595. The TLC5940 is a constant current driver. So you don't need current limiting resistors (other than IREF) and you want to keep the source voltage close to the forward voltage of the LED. (e.g. don't drive 2V Green LEDs with a 12V battery.)