That's done with the "highlights.scm" query (https://tree-sitter.github.io/tree-sitter/syntax-highlightin...) that maps nodes to their types with lots of standard names (https://github.com/tree-sitter/tree-sitter/blob/master/highl...).

The maintainer of the tree-sitter grammar is usually one who maintains that mapping. At least, every time I've wanted to use it, it's been the case that all of that was already done and part of the grammar's repo.