Unwanted color tint across the entire shot — too green under neon, too blue in shadow, too orange under tungsten. White balance or filtration fixes it.
Color Cast
You're shooting a scene and notice during playback: the entire image has a greenish hue. That's your color cast—and it's annoying because it sabotages the emotional impact of the shot. Color casts occur when the color temperature of the light source doesn't match the camera's white balance. Practically, this means: your camera thinks it's daylight (5600 K), but you're shooting under fluorescent lights (4200 K or greenish) or in the shade (7000+ K, i.e., bluish).
On set, you have three levers: Correct White Balance—this is the first choice. You measure with a gray card or use the automatic WB function (caution: only works if there's enough neutral material in the frame). Some cameras have preset WB modes for tungsten, daylight, or fluorescent—often sufficient for a quick correction. Use Filters—a 1/2 CT Blue under tungsten or a magenta filter under fluorescents optically compensates for the cast before it hits the sensor. This is cleaner because you're not electronically fiddling with the RAW data. Correct in Post—less elegant, but possible. LUTs, color grading, or simple color temperature sliders in DaVinci or Premiere fix it afterward.
The tricky cases are mixed lighting situations: windows (daylight 5600 K) meet office lighting (4200 K greenish). Here, a single white balance won't help—you'll either have to selectively stop down, adjust artificial light, or accept that different areas of the image have different casts and separate them in post. Color casts aren't always mistakes: intentional color cast (warm orange tone for nostalgia, cool blue tone for coldness) is a classic creative tool. The difference lies in control—your cast should be deliberate, not accidental.
My tip: Always take a white balance reference shot before the take. Point the camera at a gray card, focus, and save the WB. This gives you an anchor point for color corrections later in post and saves you arguments with the colorist who doesn't believe you that the light was really that green.