Thank you for your advice. After four or five reboots(*) and changing themes and cursors, all cursors are white everywhere. I noticed that every time I change the theme, the cursors resets, so the correct way to do it is to set the theme, restart(*), set the cursors, restart(*) and check everything. If there are still no white cursors everywhere, repeat.
* Logout/login seems to do the job and is faster.
