In photography, color cast is defined as:

• A. A subtle tint of one color, generally red, green or blue, that causes an image to appear unrealistic.
• B. A lens that reduces color saturation
• C. A post-processing technique to increase sharpness
• D. A filter that brightens shadows

Answer: (A)

Color cast is an overall tint in an image caused by the lighting and white balance not being neutral. That tint tends to lean toward a single color—red, green, or blue—so whites and other neutral tones start to look off, which can make the scene feel unrealistic. This description matches what photographers mean by color cast: a subtle color shift that changes the overall color balance of the image. You fix it by adjusting white balance (in-camera or in post) or by shooting in RAW so you can correct the tint later. The other choices refer to different things—saturation changes, sharpening, or a lighting filter—not a uniform color tint across the whole image.