What is deep colour?

In plain language

Standard HDMI video is 8 bits per channel: 24 bits per pixel, about 16.7 million colours. Deep colour extends that to 10, 12 or 16 bits per channel — up to 48 bits per pixel.

Why it matters in your setup

The gain is smooth gradients. At 8-bit, a sky or a slow fade steps visibly; at 10-bit it does not. HDR makes this critical, because a wider brightness range spread over 256 steps bands badly.

It costs bandwidth in direct proportion, which is why deep colour and high frame rates compete for the same budget. It also has to be advertised: a chain that does not declare deep colour gets 8-bit, and HDR either fails or bands.

What the DR HDMI 8K does with it

The DR HDMI 8K supports 4K at 10, 12 and 16-bit and up to 48-bit deep colour, and lists deep colour support explicitly in its specifications. Its EDID tables let you advertise the bit depth deliberately — 10-bit for 4K120, 12-bit for 4K60 4:2:0 — and the OLED reports the depth actually negotiated.