Once it has computed the new value to use for each of the color options, tk_setPalette scans the widget hierarchy to modify the options of all existing widgets. For each widget, it checks to see if any of the above options is defined for the widget. If so, and if the option's current value is the default, then the value is changed; if the option has a value other than the default, tk_setPalette will not change it. The default for an option is the one provided by the widget ([lindex [$w configure $option] 3]) unless tk_setPalette has been run previously, in which case it is the value specified in the previous invocation of tk_setPalette.
After modifying all the widgets in the application, tk_setPalette adds options to the option database to change the defaults for widgets created in the future. The new options are added at priority widgetDefault, so they will be overridden by options from the .Xdefaults file or options specified on the command-line that creates a widget.
The procedure tk_bisque is provided for backward compatibility: it restores the application's colors to the light brown (“bisque”) color scheme used in Tk 3.6 and earlier versions.