Scientific figure accessibility: make the encoding survive colour

The core rule: colour should reinforce meaning, not carry it alone

If two conditions can only be distinguished by hue, the figure has a single point of failure. Add another visual cue so the distinction survives changes in colour perception, printing, copying, and display quality.

• Use marker shape, line style, direct labels, or pattern in addition to hue.
• Keep important text and marks at sufficient contrast against their background.
• Check whether categories remain distinct in grayscale where print or copying matters.

Red–green is a common risk, but accessibility is broader than one colour pair

Several publishers explicitly caution against red–green distinctions, but replacing one hue is not automatically enough. Similar lightness, thin lines, and crowded legends can create other accessibility failures.

Grayscale is a useful stress test, not a complete accessibility test

A grayscale check can expose categories that collapse to similar luminance, but it does not simulate every form of colour-vision deficiency. Use it alongside colour-vision simulation, contrast checks, and redundant encoding.

Accessibility is not a claim about scientific validity

Accessible visual encoding helps more readers recover the intended distinctions in the data. It does not validate the underlying experiment or statistical analysis.

Source note

Publisher specifications are not universal and can change by journal, artwork type, and submission stage. The target journal’s current instructions remain authoritative.

• Frontiers — figure accessibility guidance
• APS — style basics and accessible colour palettes