编写一个JavaFX程序，允许用户从5个单选钮中挑选一种颜色，在一个正方形中显示相应的颜色。 报错显示找不到 符号 rect,是啊子啊不知道哪错了

#真的会疯，有没有人帮帮我

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class test6_2 extends Application
{
    public void start(Stage primaryStage)
    {
        ColorOptionsPane pane=new ColorOptionsPane();
        pane.setAlignment(Pos.CENTER);
        
        Scene scene=new Scene(pane,500,500);
        
        primaryStage.setTitle("Color Options");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
        public static void main(String[] args)
    {
        launch(args);
    }
}

import javafx.event.ActionEvent;
import javafx.geometry.Pos;
import javafx.scene.control.RadioButton;
import javafx.scene.control.ToggleGroup;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;

public class ColorOptionsPane extends HBox
{
    private RadioButton REDButton,GREENButton,ORANGEButton,YELLOWButton,BLUEButton;
    
    public ColorOptionsPane()
    {
     Rectangle rect=new Rectangle(300,300,Color.white);
        
        StackPane rectPane=new StackPane(rect);
        
        ToggleGroup group=new ToggleGroup();
        
        REDButton=new RadioButton("Red");
        REDButton.setSelected(true);
        REDButton.setToggleGroup(group);
        REDButton.setOnAction(this::processRadioButtonAction);
        
        GREENButton=new RadioButton("Green");
        GREENButton.setToggleGroup(group);
        GREENButton.setOnAction(this::processRadioButtonAction);
        
        ORANGEButton=new RadioButton("Orange");
        ORANGEButton.setToggleGroup(group);
        ORANGEButton.setOnAction(this::processRadioButtonAction);
        
        YELLOWButton=new RadioButton("Yellow");
        YELLOWButton.setToggleGroup(group);
        YELLOWButton.setOnAction(this::processRadioButtonAction);
        
        BLUEButton=new RadioButton("Blue");
        BLUEButton.setToggleGroup(group);
        BLUEButton.setOnAction(this::processRadioButtonAction);
        
        VBox options=new VBox(REDButton,GREENButton,ORANGEButton,YELLOWButton,BLUEButton);
        options.setAlignment(Pos.CENTER_LEFT);
        options.setSpacing(10);
        
        setSpacing(20);
        getChildren().addAll(options,rectPane);
    }
    public void processRadioButtonAction(ActionEvent event)
    {

        if(REDButton.isSelected())
            rect.setFill(Color.RED);
        else if(GREENButton.isSelected())
            rect.setFill(Color.GREEN);
        else if(ORANGEButton.isSelected())
            rect.setFill(Color.ORANGE);
        else if(YELLOWButton.isSelected())
            rect.setFill(Color.YELLOW);
        else 
            rect.setFill(Color.BLUE);
    }
}