Mac OS 8.5 and above technically the theming support as well (presumably salvaged from Copland), but Apple removed the themes from the final version of 8.5, and never released any of them. I'm not sure if many 3rd party ones were made either, as another commentator notes Kaleidoscope was already fairly established as the theming tool for classic Mac OS, and worked with older stuff like System 7.
[0] https://www.macintoshrepository.org/1706-kaleidoscope
[1] https://web.archive.org/web/20191021204432/https://twitter.c...