tufte-color-in-information-design
Color in Information Design
Overview
Color is a channel for transmitting data, not decoration. In Envisioning Information (Chapter 5, "Color and Information"), Tufte shows the eye is exquisitely sensitive — a trained colorist distinguishes ~1,000,000 colors under contrived pairwise tests — yet for encoding abstract information more than 20–30 colors produce not diminishing but negative returns, because the binding limit is human visual memory, not local discrimination. Even putting a good color in a good place is hard, so the governing principle is restraint:
"Above all, do no harm." — Tufte, Envisioning Information, p. 81
§1. The Four Functional Uses of Color
Every color mark serves one of four roles. Naming the role determines the correct palette strategy. Tufte reads all four off a single Swiss alpine map (the Matterhorn sheet): water distinguished from stone and glacier (label), altitude shown by contour and rate of change by darkening (measure), river blues and shadow hachures (representation), and the topography enlivened beyond what black-and-white could do (decoration).
| Role | Color Acts As | Map Example | Palette Constraint |
|---|---|---|---|
| Label | Noun — names a category | Water vs. stone vs. glacier | Primaries + black for maximum separation; few categories |
| Measure | Quantity — encodes a scalar | Altitude/depth darkening with value | Sequential value scale, light → dark; never rainbow |
| Representation | Imitates reality | River blues, shadow hachures | Match perceptual expectation: blue for water, brown for land |
| Decoration | Beauty / enlivening | Overall vitality of the sheet | Earn it from data first; never let it compete |