run next code

        HBox hbox = new HBox();
        hbox.getChildren().addAll(new Button("ONE"), new Button("ONE"), SplitMenuButtonBuilder.create().text("ONE").build());
        stage.setScene(new Scene(hbox));
        stage.show();

note that word ONE on buttons looks different then one on the SplitMenuButton

see attached screenshot and color comparison top part of E button