Photography and LED- PWM-flash ?

Hi,

I have very little experience with photography, but recently got an older DSLR-camera (Fuji Finepix S3) and a nice set of lenses.
At http://photoduino.com/ I found a nice project using sensors to operate the camera and use it for time-lapse video, highspeed triggering, etcetera.

Looking at it's gallery, Flickr: The Photoduino Pool , a lot of the "high-speed" (or just timed right) photo's seem to be shot with coloured flash-light and I wouldn't mind creating one..

I know how to light an RGB-led in a specific colour, but wonder whether the PWM-technique and short amount of time a shutter is open won't give problems. If I would set the flash to x% red, y% green and z% blue, I'd like to see about the same percentages on the photo. If the shutter is open for a longer period, that probably won't pose a problem, but I would like to know whether it could at shorter shutter times.

I personally also was very impressed when I saw a 10-watt Led burning at full-power for the first time. I know I can set sensitivity of my camera using the ISO-settings, but wonder what type of led(s) (lumens/power) would be good enough to use, if the idea of using an RGB-led and PWM is... a good one at all.