HELP! Optics for the output of an RGB LED color controller

[Biker Bear]

I haven't seen anyone mention this RGB LED controller here; it strikes me as pretty nifty. I plan to build one and have it drive 6 1w LEDs - 2 each of red, blue and green, arranged in a hexagon, the hole in the center being where the wiring will pass into the casing. The problem is ... how do I then both blend the output of the LEDs into the final color, and re-collimate the output into a somewhat directional beam? Oh, and without losing a huge amount of brightness in the process would be nice....

Obviously, I could use any of a variety of diffusers to blend the colors; it's the second phase I'm not sure how to deal with - so any suggestions would be greatly appreciated.