[djaro]

But its frequency still rose by over 300x since the start of the chart, which might suggest that for some people it is a basic color term.

"English" isn't one monolith. Every English speaker speaks their own version, some closer to each other than others, and new features are constantly being added or removed.

[vigilantpuma]

The further you have to narrow down the set of speakers for whom it's a basic color term, the less of a basic color term it is for English as a whole. We don't have to have this argument about e.g. orange.