Well I had thought I’d was rainbow gneiss but not I think it has to be banded iron formation rock. As this rock is not granite based at all.
The colors are from iron rich minerals layering. More here-
https://news.wisc.edu/banded-rocks-reveal-early-earth-conditions-changes/

https://www.geocaching.com/geocache/GC4DDNK_rainbow-gneiss