Where are GTK+ icons stored?

Solution 1:

The user added icons are in the user's home folder in a hidden folder:

• home/user/.icons

The installed icons through APT aswell as the defualt icons are in:

• usr/share/icons

The first can only be used by the user that has them, the second can be used system wide.The icons you mentioned for example are in the Humanity folder under usr/share/icons/Humanity/actions/XX (xx=size) most are in the 48 size folder and are in both .png and svg file formats and some other in ubuntu-mono-dark.

To edit them you need to use gksu

Solution 2:

The Ambiance icons (actually, Humanity + mono icons) are stored mostly in the Humanity and ubuntu-mono-dark themes.