I was wondering the same thing. The fans aren't connected to the motherboard though, so I'm not sure how that would be possible. I've only had the case for a week now so I haven't had time to tamper with it, and so far the only solution I've thought of would be to put tape over the LEDs, but that's kind of silly. Perhaps an external fan control panel could be rigged to turn them off.
Yes you can use a fan controller to limit the fan speed but not completely turn off. It is not possible to turn off the LEDs unless you are willing to do some modding and include a switch from the leads to the LEDs.