Anthropic

Anthropic's site runs on warm ivory parchment (#faf9f5) — not white, not gray, but the color of aged paper under good light. The palette is almost entirely achromatic, with the entire chromatic budget spent on a single earthy terracotta accent (#d97757) held in reserve in CSS tokens but largely absent from the visible UI. Two custom type families do all the personality work: Anthropic Sans drives navigation and UI at tight tracking, while Anthropic Serif delivers editorial weight in headlines and featured content — the serif-plus-grotesque pairing signals research institution, not startup. Headlines use a thick double-underline on key words (visible on 'research' and 'products') as the sole decorative device — it replaces color as the emphasis mechanism. The massive feature cards flip to near-black (#141413) background, creating hard-edged alternating surface bands with zero gradient or shadow softening. Use #faf9f5 (Ivory Light) as the page base — never pure white (#ffffff) or neutral gray. Apply borderRadius 0px to all buttons and interactive controls except the primary 'Try Claude' CTA which uses 0px 0px 8px 8px (asymmetric: flat top, rounded bottom only). Emphasize headline keywords with a thick text-decoration underline only — never color, bold weight increase, or highlight backgrounds — as the sole decorative emphasis mechanism. Use Anthropic Serif at display sizes (91px, weight 400) exclusively within dark (#141413) surface cards; use Anthropic Sans for all light-surface headlines. Restrict chromatic color to the CSS accent palette (Clay #d97757, Olive #788c5d, etc.) and deploy it sparingly — one accent per section maximum; default state uses zero chromatic color. Set dark editorial feature cards to borderRadius 24px and keep them full content-column width with hard clipping of interior imagery at the same radius. Use Anthropic Mono 16px for metadata field labels (DATE, CATEGORY) in card footers — the mono/grotesque contrast signals structured data within editorial layout. Never use pure white (#ffffff) or pure black (#000000) as a surface background — all surfaces must come from the ivory/slate token range. Never add box-shadows or drop-shadows to any component — surface contrast and border lines are the only depth signals. Never round button corners uniformly — the 0px radius is a deliberate formal signal; avoid introducing 4px, 6px, or pill buttons. Never use Anthropic Serif on the page's ivory background at large sizes — the serif display scale is reserved for the dark card inversion. Never apply multiple chromatic accent colors within a single section — the palette tokens (Clay, Sky, Fig, Olive) are categorical variants, not combinable accents. Never use background fills for badge or label components — metadata labels are pure text with no chip, pill, or capsule treatment. Never replace the underline emphasis mechanic with color emphasis on headlines — links within headlines underline, they do not change color.