Colour Balance uses an iPhone's front camera to measure what the TV displays from a series of colour swatches, then corrects the Apple TV's video output so colours look as the creators intended. It changes only the Apple TV's output signal — it does not touch the TV's own picture settings, and it doesn't create a profile you can export.
Requirements: Apple TV HD or any Apple TV 4K generation, an iPhone with Face ID (iPhone X or later) on iOS 14.5+, and Dolby Vision must be off on the Apple TV while calibrating.
What to expect: on a TV at factory settings the improvement is usually visible — skin tones and colour cast get noticeably more neutral. On a TV that's already professionally calibrated, the change is much smaller, because the panel is already accurate; the calibration mostly compensates for the panel's remaining error. It's a convenience feature, not a replacement for display calibration.
Note it calibrates for the connected display: re-run it if you move the Apple TV to a different TV.
Sources: https://support.apple.com/guide/tv/atvb228b7711/tvos
— Osnivo Guides