Suggestions for purple RGB LED?

Yes, I know the purple question has been discussed elsewhere.
That's not exactly what I'm asking about.

Since the Ultrasound 2.1 just got shipped out, and since there is no tutorial yet on MR white flash clash with a custom tri-rebel, nor is there availability of the CF that I can find, I was thinking of making my custom purple MHS using the US 2.1 board.

That way, at least I would get all the sounds and even blade flicker, which would be fine with me. I can always tackle the white clash flash thing once the tutorial comes out or Erv gets more supply of the CF and powerextender boards.

My question really is the following -
I'm using 2 trustfires for, what, 7.4V? to power the US 2.1 . Originally, I had gotten the trustfires so they could be used with a royal blue LuxV. But since I wanted to use the US now for the purple LED, I thought, hey, well, why don't I just use the trustfires instead? Here's the rub.. I was originally going to use a Seoul 3.5W RGB to get the purple I needed. Seemed to be doing ok with 6V (4AAA) with the blue and red in series off a 700mA buckpuck...
But when trying to run it off of the US board on the LuxV setting, I lose the purple color and get a really intense blue (which I suspect will blow the LED pretty soon). I think the voltage may be way over what the Seoul wants, so I was wondering if anyone has a suggestion on what RGB (or combo LED thereof) one would use with this setup (US 2.1 + 2 trustfires) and how to wire it / board setting?? I don't mind getting another LED or changing the board settings.

The only thing I could think of was maybe an LEDengine or perhaps Tri-Rebel... I know MadHatter did something similar with a 10W LEDengine I think and a CF board with 7+V of power.

sorry if this sounds like a silly question...