One colour carries heat across every Ordova surface, and it is spent carefully. Elsewhere the accent rides only the live path; in this room it marks only how recently a record was filed. Warm nodes cool to open outlines as they descend the spine, and the freshest stamp is the only one struck in colour.

The rule earns its keep by what it forbids. Nothing decorative may take the accent, so when the accent appears it is information, not ornament. A visitor who learns the rule once can read every page after it.