@kate just discovered it, very impressive!
Did you use HSL and then adjust luminance by hand? I wonder if LCH or OKLCH is easier to use for this sort of stuff, as its L component already corresponds to the perceived light.
Colour picker: https://oklch.com/#70,0.1,77,100
About OKLCH in CSS: https://evilmartians.com/chronicles/oklch-in-css-why-quit-rgb-hsl