Check the measuring device
Apple’s Color Balance tool uses an iPhone with Face ID and iOS 14.5 or later. A phone that can act as an Apple TV remote does not automatically meet those measurement requirements. Check the iPhone model and installed system before arranging the calibration.
On Apple TV 4K, the tool is under Settings, Video and Audio, Calibration. Follow the current on-screen prompts rather than copying camera positions from an unrelated television calibration app. The box and the measuring phone are participating in a specific supported procedure.
Give the comparison a stable setting
Keep the television on the same input and picture mode during the measurement and its before/after comparison. Changing the TV’s picture mode at the same time creates another variable. Use familiar material afterwards and decide whether the adjusted output meets your preference.
Color Balance belongs to the Apple TV viewing route. Do not infer that a measurement has calibrated a game console on another input, fixed a wrong programme source or certified the panel against a professional reference. Those are different questions.
Use the right calibration tool
Apple places Color Balance beside other calibration tools, including a Zoom and Overscan reference and Color Bars. If the problem is clipped picture edges, a colour measurement is not the first relevant check. Describe the visible problem before choosing the tool.
Keep a short note of the TV picture mode and whether the adjustment was accepted. That is enough to make a later comparison meaningful without presenting a subjective viewing preference as an instrumented display review.
Questions answered
Will any iPhone work?
Apple specifies an iPhone with Face ID running iOS 14.5 or later.
Does Color Balance correct cropped picture edges?
Cropping is a separate picture-fitting problem. Apple provides a Zoom and Overscan reference for that task.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.