Color-blind safe palette design

The problem

Red-green encoding fails for ~8% of males. Status indicators, heatmaps, and categorical charts collapse into indistinguishable blobs when hue alone carries meaning. The fix is not desaturation — it is deliberate contrast in luminance and shape.

Safe palette (6 stops)

Based on the Wong 2011 Nature Methods palette. Works for deuteranopia, protanopia, and tritanopia without modification.

Rules

• Never rely on hue alone — pair with pattern, label, or luminance delta.
• Test every chart in greyscale first. If it works without color, it works for everyone.
• Avoid red-green as the only differentiator for binary states.
• Use direct labels on data points instead of legends when possible.

Quick test

Paste your screenshot into Coblis or use Chrome DevTools rendering emulation. If any two categories merge, add a luminance gap of at least 30 points in HSL.