Colorduino PWM rate

When I first got my Colorduinos with their inbuilt demo firmware I could video them with no problem.

Now I have loaded some firmware onto them to run them using I2C. That works fine, I can use my Mega 2560 to talk to the Colorduinos and do some nice displays. But now videoing them is really messy, flickering with lots of black lines moving around. This I guess is because of the PWM rate that the Colorduinos are now using.

Does anyone know how I can change the PWM rate on the Colorduinos so I can find a rate that will not interfere with a video running at 50 or 60 frames per second?

Thanks, Steve