java - How to modify MenuButton arrow color by JavaFX not FXML CSS? -

i trying modify color of menubutton arrow , using javafx code not css.

i found inside caspian.css :

.menu-button > .arrow-button > .arrow {     -fx-background-insets: 1 0 -1 0, 0;     -fx-background-color: -fx-mark-highlight-color, -fx-mark-color;     -fx-padding: 0.25em; /* 3 */     -fx-shape: "m 0 -3.5 v 7 l 4 -3.5 z"; } 

i tried use :

menubutton.lookup(".arrow"); 

but throw nullpointerexception

and when :

system.out.println(this.getstyleclass().tostring());

it out put only: menu-button only.

so can 1 give me way modify using java without using css ??

this works:

import javafx.application.application; import javafx.scene.scene; import javafx.scene.control.menubutton; import javafx.scene.control.menuitem; import javafx.scene.layout.stackpane; import javafx.stage.stage;  public class redmenubutton extends application {      @override     public void start(stage primarystage) {         final stackpane root = new stackpane();         final menubutton menubutton = new menubutton("menu");         menubutton.getitems().addall(new menuitem("item 1"), new menuitem("item 2"), new menuitem("item 3"));         root.getchildren().add(menubutton);          final scene scene = new scene(root, 250, 150);         primarystage.setscene(scene);         primarystage.show();          menubutton.lookup(".arrow").setstyle("-fx-background-color: red;");     }      public static void main(string[] args) {         launch(args);     } } 

update: better solution (which have got first time if daylight savings hadn't messed sleep ;)).

import javafx.application.application; import javafx.scene.scene; import javafx.scene.control.menubutton; import javafx.scene.control.menuitem; import javafx.scene.layout.stackpane; import javafx.stage.stage;  public class redmenubutton extends application {      @override     public void start(stage primarystage) {         final stackpane root = new stackpane();         final menubutton menubutton = new menubutton("menu");         menubutton.getitems().addall(new menuitem("item 1"), new menuitem("item 2"), new menuitem("item 3"));         root.getchildren().add(menubutton);          menubutton.setstyle("-fx-mark-color: red");          final scene scene = new scene(root, 250, 150);         primarystage.setscene(scene);         primarystage.show();     }      public static void main(string[] args) {         launch(args);     } }