To reproduce run following code
Unexpected red line around scrollbar.

import javafx.application.Application;
import javafx.geometry.BoundingBox;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.CheckBox;
import javafx.scene.control.Label;
import javafx.scene.control.RadioButton;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TextBox;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class ScrollPaneSample extends Application {

    public static void main(String[] args) {
        launch( args);
    }

    private Parent getContent() {
        VBox box = new VBox();
        ScrollPane pane = new ScrollPane();
        HBox hbox = new HBox(20);
        VBox vbox1 = new VBox(10);
        vbox1.getChildren().addAll(new Label("one"), new Button("two"), new CheckBox("three"), new RadioButton("four"), new Label("five"));
        VBox vbox2 = new VBox(10);
        vbox2.getChildren().addAll(new Label("one"), new Button("two"), new CheckBox("three"), new RadioButton("four"), new Label("five"));
        hbox.getChildren().addAll(vbox1, vbox2);
        pane.setContent(hbox);
        pane.setStyle("-fx-background-color: red;-fx-border-color:green;");
        pane.setFocusTraversable(false);

        box.getChildren().add(pane);


        return box;
    }

    public void start(Stage stage) {
        stage.setX(100);
        stage.setY(100);
        stage.setWidth(300);
        stage.setHeight(300);
        Scene scene = new Scene(getContent());
        stage.setScene(scene);
        stage.setVisible(true);
    }
}