How to return the default value for EditorStyles.toolbarButton.normal.background ???

Good afternoon.
I changed the script variable EditorStyles.toolbarButton.normal.background.

GUIStyle td = EditorStyles.toolbarButton;
td.normal.background = customBackground;

Now I can not return to the initial value EditorStyles.toolbarButton.normal.background.

Help me please !

Save the original texture into a variable:

GUIStyle td = EditorStyles.toolbarButton;
var originalBackground  = td.normal.background;
td.normal.background = customBackground;

Then when you want to recover the original assign it back.

td.normal.background = originalBackground;