· Interface
A decorative wash anchored to the theme's own accent
The calm surfaces carry a faint field of the current theme's accent. Only the surfaces a person passes through get it, never the ones they sit on all day.
The wash is drawn from the active theme's accent rather than from a fixed brand colour, so it moves with the palette instead of fighting whichever one you chose.
Where it goes is the decision that mattered. A decorative colour wash belongs on a surface someone passes through: first run, a feed, an empty state. A page of controls someone sits on all day stays plain. Both sets are pinned by test, including the pages that are deliberately undecorated.
Every ink tier is held above its contrast floor on all seventeen faces with the wash applied, and the check measures the rendered pixels rather than the stylesheet. The wash only exists once something composites it.