Colour cast

Shoot under a warm bulb with the camera set for daylight and everything goes orange. Sit under office fluorescents and skin goes green. A cast is uniform across the frame, which is what separates it from a colour problem in one part of the shot, and your eye adapts to it on set long before the camera does. Fix it at the source where you can, by matching your lights and setting white balance off a grey card. In the edit you correct it by neutralising something you know should be neutral, a white shirt or a grey wall, and letting the rest of the image fall into place.