OKLCH (Web Colour Notation)
OKLCH is a way of writing colours in CSS that describes a colour by perceived lightness, chroma and hue angle instead of red, green and blue components. It is defined in the W3C standard CSS Color Module Level 4 alongside oklab() and is supported in current browsers.
In practice
For decision-makers the effect matters more than the syntax: because lightness is controlled separately, a brand colour can be stepped into variants for hover states, backgrounds and borders that genuinely look evenly lighter or darker. Doing the same arithmetic on hex values often produces tones that visibly drift towards grey or become garish. It also simplifies contrast checking, since you can adjust one value until the contrast passes without losing the hue. You need not insist on OKLCH, but do ask how colour steps are generated: hand-maintained hex lists are a classic source of inconsistency. A hex fallback remains sensible for very old browsers.