Contrast Palette Grid

In short A contrast grid takes a whole palette and tests every colour against every other one, marking each pair as safe for body text, large text, interface elements or nothing. Checking pairs one at a time answers the question you thought to ask; checking the full matrix answers the ones you did not — and the pair that fails is almost always a combination nobody deliberately chose, like a muted label on a tinted card, or a border that only appears in one state. The thresholds are the WCAG ones: 4.5:1 for body text at AA, 3:1 for large text at 24px or 18.66px bold, 3:1 for interface components and meaningful graphics under criterion 1.4.11, and 7:1 for AAA. The interface figure is the one most often missed, because people check their text and never check their input borders or their focus rings. Two honest limits. The ratio is a luminance calculation and knows nothing about hue, so it will approve two colours of similar brightness and very different colour as identical, and it will fail some pairs that read perfectly well. And a grid past about fourteen colours stops being readable, which is usually a sign the palette itself needs trimming.