Simulating Colour Blindness with ImageMagick
Colour blindness affects roughly 8% of men and 0.5% of women with Northern European ancestry. For a data visualisation that uses colour as the primary encoding — a choropleth, a multi-series line chart, a heatmap — that’s a meaningful share of the audience for whom the visual may be conveying the wrong information, or none at all.
The right time to test this is during design, not after a complaint. ImageMagick’s -color-matrix flag lets you simulate the major forms of colour vision deficiency directly on any image — screenshots, design exports, chart renders — from the command line. This makes it scriptable, batchable, and easy to drop into a CI pipeline alongside screenshot tests.