A palette's accent is not one value, it is a family: the seed plus the soft
surfaces mixed from it — seven slots per appearance in nous, all derived
from one colour. `retintTheme` moves the whole family at once, reusing the
converter's own mix ratios so re-seeding a theme with its existing accent
returns the identical object.
The colour work this needed is the interesting half. Mixing toward white in
gamma-encoded sRGB bends hue: a saturated blue lands 7.6 degrees violet of
where it started, which is how a clean blue accent produced a lavender
selection row. `mixOklab` holds the hue and moves only chroma and lightness.
`ensureContrastOklch` adapts a seed for an appearance that cannot carry it
by walking lightness rather than blending toward white, which would gut the
chroma and wash the brand colour out.
`readableOn` picked text colour from a luminance threshold, and got five
shipped accents wrong in the direction that matters — white on GitHub's own
dark green measured 3.29:1, below AA, where near-black measures 5.50:1. It
now measures both candidates and takes the better one.
Brooklyn Nicholson
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