Finally figured it out.
All the permissions in the template files are set to 644. Changed to 777 to make the changes. (Change back when done.)
Changing params.ini file in the /templates/ja_PureSite folder fixed the error “An error has occurred when saving Global Settings;
Changing default.ini in the /templates/ja_PureSite/etc/profiles folder fixed the error “An error has occurred when saving default profile.”
Seems to be the same problem I’ve read about across a number of Joomlart templates. You’d think somebody would make it easier to simply switch the color scheme, as in the demos.
Also, do check that ftp is set correctly and if Apache owns the files (which it didn’t on my system), chown to the ftp user.