It may not have a zillion libraries, but surprised that a site trying to be zippy uses low-contrast text (obviously, I am not a fan of the "increases engagement time" school of thought).
Could be because I'm reading on desktop and it works better on mobile.
He is using, as far as I can tell, the solarised theme colours.
They are very readable.
[EDITED] https://www.rundata.co.za
It's my site, also using solarised (although, it respects the clients dark/light mode, so you will see either solirsed dark or solarised light)