Colour
Six brand colours from the guide, a family of derived neutrals, and one added error colour. Petrol is the flag; vermeil is rationed to one appearance; porphyry is reserved. The rest is warm parchment and cool grey.
The primary ground and the heading colour. 12.2:1 on white, 11.6:1 on parchment, 10.5:1 on limestone — AAA everywhere as text. Heroes, the footer, and one institutional band per page.
The single accent. The cross in the mark, a 48×2 rule under a heading, the motto in italic — one of them per composition, never a field. As text it fails on every light ground (3.37:1 on white, 2.89:1 on limestone) and reaches only 3.62:1 on petrol, so gold type is display at 22px or larger, on petrol only.
The light ground where warmth is wanted: a set-apart section, the reversed lockup’s letter, headings on petrol. It replaces white wherever white would feel clinical.
All running text on light grounds, and the one-colour mark for engraving. Warm black, 16.2:1 on parchment.
The stone of emperors and patriarchs. Regalia, and rare moments of gravity — the pull quote, once per site. 10.5:1 on white as text, but it is not a text colour; it is a ground used sparingly, and the hover colour of a link.
The page ground
Table heads, inputs
Every hairline
Decorative only, 3.75:1
Captions, meta, 5.65:1
Hover of a petrol fill
Parchment, Field and Rule are the guide’s own page ground, table tint and rule colour, promoted to tokens. Sand is the guide’s caption colour and fails AA for text, so Umber — the same hue two steps darker — carries captions. The greys lean cool so they keep their distance from the warm grounds.
The guide has no error colour and its only red, porphyry, is spoken for. Cinnabar is separated from porphyry by chroma, not hue: porphyry is muted (oklch C 0.10), Cinnabar vivid (0.18), 23° warmer — so it reads as an alert rather than as more regalia. 6.57:1 on white, 6.25:1 on parchment, 5.63:1 on limestone. An error carries three signals: the rule, the tint, and an icon.
One hard limit: Cinnabar on petrol is 1.86:1 and fails. An error never appears inside a petrol band — forms live on parchment, limestone or white.