color-expert

color-expert

An agent skill that turns your coding agent into a color science expert. Built from resources I keep looking up, returning to, and sharing with others.

What this is

This started as a simple skill file with some color theory notes. Over time it grew into a comprehensive knowledge base as I kept pasting videos, articles, tools, and papers that I find myself referencing again and again — both for my own work building color tools and for explaining color concepts to others.

The skill has three layers:

1. SKILL.md — The "greatest hits" that your agent loads immediately. Key facts, corrections, tool recommendations, and guidelines that answer most color questions without needing to dig deeper.

2. references/INDEX.md — A compact map, one line per reference file, meant to be read whole when the agent needs to find the right file. Full summaries and source links live in per-directory indexes (references/*/INDEX.md) that are only opened when the one-liner is too terse to choose.

3. references/ — Deep reference material: full video transcripts, article summaries, library documentation, scraped websites, and research notes.

There is also a lightweight evals/ folder for realistic trigger and task prompts so the skill can be reviewed against actual usage instead of only edited by intuition. evals/TRIGGERING.md states the rule those trigger cases encode, so the boundary is arguable in writing rather than per-case.

How it was built

The collection process is simple: when I come across a color resource worth keeping — a YouTube video, a GitHub repo, a research paper, an article — I paste the URL and the skill's workflow captures it:

• Videos get transcribed via yt-dlp, summarized, and key concepts extracted
• PDFs and documents get converted to markdown via markitdown by Microsoft
• GitHub repos get their README/docs fetched and documented
• Articles get their content extracted and saved
• Books mentioned in videos get searched on Archive.org; freely available PDFs get downloaded
• Websites (like huevaluechroma.com) get fully scraped chapter by chapter
• Tools and links mentioned in any resource get collected into the Online Tools table

Everything goes into one of three folders and gets indexed.

Structure

SKILL.md                              # The skill definition (loaded on activation)
CLAUDE.md                             # Claude Code repo instructions
references/
  INDEX.md                            # Compact map: one line per reference file
  PDFS.md                             # Primary-source PDFs (gitignored, archive.org links)
  historical/                         # Pre-digital color science
    INDEX.md                          # Full summaries + sources for this directory
    *.md                              # Ostwald, Helmholtz, Bezold, Ridgway, ISCC-NBS,
                                      # Moses Harris, Amy Sawyer, Lewis/Ladd-Franklin,
                                      # Caravaggio's pigments, Itten critique...
    pdfs/                             # Source books from Archive.org (gitignored, see PDFS.md)
  contemporary/                       # Modern color science & theory
    INDEX.md                          # Full summaries + sources for this directory
    *.md                              # OKLAB articles, Briggs lectures, CSA webinars,
                                      # Pixar Color Science, bird tetrachromacy, OLO,
                                      # Acerola, Juxtopposed, Computerphile, GenColor paper...
    huevaluechroma/                   # Full scrape of David Briggs's site (11 chapters)
    colorandcontrast/                 # colorandcontrast.com extracted content
    pdfs/                             # Research papers (gitignored)
  techniques/                         # Tools, libraries, methods, practical application
    INDEX.md                          # Full summaries + sources for this directory
    ONLINE-TOOLS.md                   # Pickers, generators and analysers, with what each is for
    *.md                              # Spectral.js, Culori, Color.js, RampenSau, Poline,
                                      # RYBitten, PickyPalette, Color Buddy lint rules,
                                      # APCA/Myndex, IQ cosine formula, Cubehelix,
                                      # Tyler Hobbs generative color, Fontana approach,
                                      # pixel art palettes, Book of Shaders, LYGIA,
                                      # paint mixing lecture, color harmony lecture...
evals/
  TRIGGERING.md                       # The rule the trigger cases encode
  trigger-evals.json                  # Realistic should-trigger / should-not-trigger prompts
  task-prompts.md                     # Realistic color tasks for qualitative review
scripts/
  stats.sh                            # Source of every count quoted in this README
MAINTENANCE.md                        # What belongs where, source quality bar, review rubric
ROADMAP.md                            # Planned scripts and future extensions

Reviewing the skill

The repo now includes a minimal review loop rather than a heavy benchmarking framework:

1. Use evals/trigger-evals.json to sanity-check whether the frontmatter description is likely to trigger in the right situations, and evals/TRIGGERING.md when a case looks arguable.
2. Use evals/task-prompts.md to test whether the skill answers realistic color questions at the right level.
3. Use MAINTENANCE.md when deciding whether something belongs in SKILL.md, references/, or not in the repo at all.
4. Use ROADMAP.md to track planned color-specific scripts and larger repo improvements.

What's in it

By the numbers

Counted at the last update; run bash scripts/stats.sh to refresh rather than trusting these.

Historical color science

The resources I keep returning to when explaining where color theory came from and where it went wrong:

• Ostwald (1918–1930) — the 24-hue perceptual circle that dominated the 1930s–40s then disappeared
• Helmholtz (1856) — foundational physiological optics; last major physicist to use "indigo"
• Bezold (1874) — killed indigo as a spectral color; renamed it "ultramarine blue"
• Ridgway (1912) — 1,115 named colors for naturalists; fully digitized as JSON
• ISCC-NBS (1955) — 319 systematically named color blocks
• Moses Harris (1769) — the origin of bad RYB color theory (his own wheel needed a 4th pigment)
• Amy Sawyer (1911) — patented a CMY wheel decades before it was mainstream
• Elizabeth Lewis (1931) — married trichromatic + opponent process, anticipating CIE Lab/Luv by decades
• Plus: Caravaggio's copper resinate technique, Itten's seven contrasts (critically reviewed), the evolution of "magenta" as a color name, Frank Reilly's controlled palette

Contemporary color science

The theory and science I reference when building tools or explaining why things work the way they do:

• Bjorn Ottosson's OKLAB articles — all four foundational posts (OKLAB, color picker spaces, gamut clipping, "how software gets color wrong")
• David Briggs's huevaluechroma.com — fully scraped, 11 chapters + glossary
• colorandcontrast.com — UI-focused color science reference, extracted from SPA bundle
• Color Nerd (Peter Donahue) — 20+ video transcripts covering mixing paths, spectral perception, warm/cool, chroma vs saturation, bird vision, OLO
• **Colour Society of Aust