Note delete confirmation dialog should have the "destructive-action" style class set on its deletion confirmation button
Partially a stylistic issue but also for usability, that button should have the "destructive-action" CSS class set on it. See also https://developer.gnome.org/hig/patterns/controls/buttons.html#button-styles
There might be other dialogs where destructive-action
or suggested-action
can be used in Tomboy, but I'm not sure where they are...