Why does Display Information show both 10-bit and 8-bit color?

The two values can describe different stages of the display pipeline. Current Display Mode reports the rendering mode, while Current Display Mode (Connection Level) reports the format sent toward the display. A 10-bit rendering surface can feed an 8-bit connection.

Under Current Display Mode, Bits per sample describes the precision of each stored color component. Bits per pixel is a different quantity that includes multiple components and may include additional storage. Under Current Display Mode (Connection Level), Bit Depth describes the connection’s bits per sample. See bit depth for these units.

For the format travelling over the connection, use the connection-level value. Neither value tells you the panel’s native precision or exactly how the image will look. A monitor described as 8-bit + FRC uses frame rate control inside the monitor to approximate intermediate tones. That is separate from the Mac’s rendering surface and transport format.

Dithering can also approximate intermediate tones when a higher-precision image is sent through a lower-precision path. GPU-side dithering and the monitor’s own processing are separate stages. A 10-bit rendering mode can still use an 8-bit connection. An 8-bit connection can produce a smooth image with dithering.

If you want a different connection format, inspect the supported choices in Color Mode at the current resolution and refresh rate. Choose from the formats the connection offers. See Color Mode and GPU dithering settings. Changing the GPU setting does not turn off processing inside the monitor.