Any of the settings done within the nvidia-settings that require writing to the /etc/X11/xorg.conf file, require you to be root when you edit those settings, then click on SAVE. However, there are a lot of monitor type configuration settings that can be made by individual users, without being root.
Those settings are stored in ~/.nvidia-settings-rc in your user home folder. However, they do not automatically load when you log in to your desktop session. For that to happen, you need to go into your Sessions and Startup utility, and create a new entry in the autostart section. The command to use is:
With that done, when you log in to your session, your digital vibrance setting, and any others, should be restored as you configured them.
---------- Post added at 03:00 PM ---------- Previous post was at 02:51 PM ----------
BASH:~/-> grep DigitalVibrance .nvidia-settings-rc