TLDR: oklch() is a new CSS color format, improving over RGB and HSL by offering better perceptual lightness, chroma and hue definitions for colors, enabling automatic palette generation and supporting wide-gamut P3 colors. It offers enhanced readability, predictable lightness for color modifications, and greater accessibility. While OKLCH is young and faces ecosystem limitations, it outperforms HSL and RGB in accuracy and usability for modern design.
https://evilmartians.com/chronicles/oklch-in-css-why-quit-rgb-hsl