Why a medium grey ground is hard

Light pages put their contrast below the ground and dark pages put it above. A medium grey has both directions open and neither of them far, which is why almost nothing is built on one.

The consequence turns up first in the accent. Forcing a warm oxide to four and a half to one against this ground drags it to something like #580000 — which reads as dark brown, not as a signal. So there is one accent and it is only allowed at display size, on rules and marks, and body text is never that colour.

The second consequence is that every step of the ramp has to be a real perceptual step. The greys here are one OKLCH ramp at a fixed warm hue, so a mix between any two of them stays warm instead of drifting through mud on the way.

What you get for the trouble is a page the 3D can actually stand in. Lit plaster against a wall of the same material is a room; the same object on white is a product photograph.