Light mode text: oklch(37.3% .034 259.733)
Dark mode text: oklch(87.2% .01 258.338)
Background in both modes: oklch(14.5% 0 0)
See here: https://jsfiddle.net/kmtwf4g3/
I think the fuckup of the website author is that the background is black instead of white in light mode. Otherwise the text colors would be fine as they are. Probably vibe coded and never tested in light mode.