Problem

postcss-colormin used colord to minify CSS color values. colord rounds color values to integers at parse time, so HSL conversions accumulate rounding error — making some RGB → HSL round-trips lossy:

rgba(221, 221, 221, 0.5) → hsla(0,0%,87%,.5)
# round-trip back: rgb(222, 222, 222) ≠ rgb(221, 221, 221) ❌

This caused visible color seams at image/UI boundaries.

Real-world impact:

• Tailwind CSS users reported production builds showing different colors than development: tailwindlabs/tailwindcss#11716
• Next.js worked around it by disabling colormin entirely — giving up all color minification to avoid the lossiness

colord also returns isValid: false for oklch(), oklab(), hwb(), and other modern CSS color formats, so gradient color stops using these formats were not recognised by postcss-minify-gradients.

colord has not received any updates since August 2022.

Solution

Replace colord with @colordx/core, its actively maintained successor with an intentionally compatible API.

colordx stores color values as floats internally — no rounding at parse time. This preserves exact precision through conversions so the minifier always picks the shortest truly lossless representation:

/* With colord (integer rounding): */
rgba(221, 221, 221, 0.5) → hsla(0,0%,87%,.5)        /* shorter but lossy ❌ */

/* With colordx (float storage): */
rgba(221, 221, 221, 0.5) → hsla(0,0%,86.7%,.5)      /* shorter and lossless ✅ */
rgba(50%, 50%, 50%, 0.5) → hsla(0,0%,50%,.5)        /* shorter and lossless ✅ */

With this fix, Next.js could re-enable colormin and recover the minification savings they gave up.

Changes

• postcss-colormin: swap colord → @colordx/core@^2.0.1
• postcss-minify-gradients: swap colord → @colordx/core@^2.0.1

Additional improvements

• oklch(), oklab(), and hwb() values within the sRGB gamut are now correctly minified by postcss-colormin (previously passed through unchanged)
• Modern CSS color formats are now correctly recognised as valid gradient color stops in postcss-minify-gradients

Testing

• Added lossless round-trip regression tests for [Bug]: colormin is lossy, colors in minified builds don't match development #1515
• Added passthrough/recognition tests for oklch, oklab, hwb, lch, color() in both packages
• 49/49 postcss-colormin unit tests passing
• 46/46 postcss-colormin integration tests passing
• 63/63 postcss-minify-gradients tests passing

Fixes #1515