https://hypercolor.dev/generator
linear-gradient(to right, rgb(185, 28, 28), rgb(234, 179, 8), rgb(21, 128, 61))
StamenMap base tiles are getting migrated to StadiaMaps https://maps.stamen.com/stadia-partnership/. The tiles were updated with https://docs.stadiamaps.com/guides/migrating-from-stamen-map-tiles/.
Map geojson is from Cartography Vectors.
These are individual files and combined in regions with geojson-merge.
$ npm install -g @mapbox/geojson-merge
$ geojson-merge file.geojson otherfile.geojson > combined.geojson
Remember to set a region label for the combined data.
https://docs.google.com/presentation/d/1Tuu63rpX-oLW08p_5uwDf3p7yPBJ1ZLn/edit#slide=id.p1