Your agent thinks HSL is fine. This 286,000-word skill disagrees.

What it does

skill.color-expert is an agent skill that injects color science expertise into coding assistants like Claude Code, Cursor, and Copilot. It loads a ~200-line “greatest hits” brief (SKILL.md) immediately, then points agents to a 144-file reference archive spanning historical color theory, contemporary science, and practical tools. The collection includes transcribed YouTube lectures, scraped websites like David Briggs’s huevaluechroma.com, research papers, and digitized books from Archive.org.

The interesting bit

The project is as much a curation engine as it is a knowledge base. The author built a capture workflow—yt-dlp for videos, markitdown for PDFs, scrapers for websites—that ingests resources and automatically files them under historical, contemporary, or technique buckets. It even includes a minimal review loop with trigger evals and task prompts to sanity-check the skill against actual usage.

Key highlights

• ~286,000 words across 144 markdown files, including 54+ transcribed videos and 14 source PDFs
• Strong, sourced opinions baked in: prefer OKLCH over HSL, avoid coolors.co, and treat hue-first harmony as a weak heuristic
• Covers niche historical ground (Ostwald, Bezold, Ridgway, Amy Sawyer’s early CMY wheel) alongside modern tooling (Culori, Color.js, Spectral.js, APCA)
• Includes accessibility research citing a brute-force run over ~281 trillion hex pairs for WCAG and APCA compliance
• Lightweight review loop with trigger evals and task prompts instead of heavy benchmarking

Caveats

• The 14 source PDFs and some scraped content are gitignored (~236MB), so the repo itself is only part of the picture
• The skill was “vibe-coded” by the author’s own admission, so the automation scripts may be pragmatic rather than elegant

Verdict

Grab this if you want your agent to explain why pigment mixing isn’t simple subtraction or to generate palettes using something better than HSL. Skip it if you just need a one-off hex code—this is a reference library, not a shortcut.