OKLCH is a colour space that offers up to 50% more colours than sRGB - more at Smashing Magazine here.
There's an amazing colour picker at oklch.com.
And a great contrast checker at oddcontrast.com
Inspired by Adam Argyle's colour palette with OKLCH gui challenge, I developed a whole paletter designer - slide the slider, tweak the individual values, copy the swatch, copy the whole palette, and have fun!
Copy a swatch and you get: `oklch(99% 0.05 320)`.
Copy the whole palette and you get:
--swatch-1: oklch(99% 0.05 320);
...etc...
--swatch-9: oklch(5% 0.1 320);