Accessible viz encodes values as redundant channels: position, pattern, label, not hue alone. Ishihara plates 1917; WCAG 2 contrast; Okabe–Ito palettes for deuteranopia.
In reports, ads and assignments it fits public dashboards, exams, print in grey, legal slides. Skip it when relying on red/green alone to mean bad/good.
Principles
- Encoding — Accessible viz encodes redundant channels: position, pattern, label, not hue alone.
- History — Ishihara plates 1917; WCAG 2 contrast; Okabe–Ito palettes for deuteranopia
- Fit — public dashboards, exams, print in grey, legal slides
- Shared baseline — The eye compares length and position more accurately than area.
- Audience — PowerPoint, Excel or Google Sheets and Meta, Google and retail print share the same geometry.
Misconceptions
- Pretty equals true — Decoration rarely persuades; it slows reading.
- 3-D helps — Perspective distortion wrecks comparison. Keep it flat.
- More series is richer — Do not stack stories. One Accessible viz, one claim.
- Default palette is fine — Rainbow defaults fail color-blind viewers and grey print. Change Excel or Google Sheets defaults.
Why it matters
- Work — Work: public dashboards, exams, print in grey, legal slides. Readable in four minutes in PowerPoint.
- Ads — Ads: one number and one shape speak first in Meta, Google and retail print.
- School — School: for lab reports and poster boards, pick the form that answers the rubric.
- Craft — Craft: honour redundant channels: position, pattern, label, not hue alone and decoration falls away.
Accessible viz: honour redundant channels: position, pattern, label, not hue alone, and switch when relying on red/green alone to mean bad/good.