Video quality troubleshooting
Chances are you don't have enough light or the light is poor quality. High frame rates require very short exposures. You are trying to capture something fast after all.
You have a choice of natural and/or artificial light.
Natural sunlight works best and the camera is white balanced for daylight. When possible, this is your best option.
Artificial light has 120Hz flicker due to our 60Hz AC power. All lights running on 120V 60Hz AC (CFL, fluorescent, tungsten, halogen and even LED's) will flicker to various degrees. Your eye can't see the flicker, but the camera can.
Depth of field and focus
Back to the lighting issue, you are likely to be using some really short exposure times and your lens will be wide open. In this case, DOF is really small and focus is critical.
When was the last time you were outside, in full sun shooting F1.4? When you are trying to stop a bullet in flight, and have the exposure set to 1/100,000 sec, you will.
The camera is white balanced for 5000K. Artificial lights may look yellowish. GE 6500K Daylight CFL's look pretty good. Beware of flicker.