This seems to be a reskin of the prior RDoc styles, which are visible in prior Ruby versions (e.g https://docs.ruby-lang.org/en/3.3/). Despite the rather bold green, the overall look of the primary content feels very subdued. I think a big part of it is how low-contrast the code blocks are. In the prior style, code blocks used a pretty high-contrast syntax highlighting scheme; comments were very distinct, which is important as these demonstrate return values. In the new style, it's quite difficult to distinguish comments (medium gray) from identifiers (dark gray).
Personally I prefer the look of rubyapi.org over either of the official ones, but this new one kinda feels like a step backward from the prior one.
Personally I prefer the look of rubyapi.org over either of the official ones, but this new one kinda feels like a step backward from the prior one.