Zettelkasten is a manifestation of Yellow. But of course, today Zettelkasten is interpreted and is used by different stages.
Many of PKM users are Orange—their reason for using Zettelkasten is productivity and higher performance. The promise of Luhman’s mythical productivity (tons of books and papers published) preaches well to this audience.
Orange users tend to use Zettelkasten to manage information on their projects (limited scale compared to Yellow’s grandiose-scale thinking).
They might try to merge project management and todo lists with knowledge management. GTD also advocates for having a single tool / flow for everything (cite?). For Orange, it’s all a part of getting things done (so it makes sense to track this in one place).