Changing style in javaFX does not do anything

Question

I made a NavigationBar fxml document, and linked that to a NavigationController class. I've managed to change scenes when pressing the different buttons, but I want to make the button of the current scene focused/different color. However, when I change the style nothing happens.

This is my NavigationBar:

    <HBox alignment="CENTER_LEFT" prefHeight="43.0" prefWidth="600.0" spacing="10.0" BorderPane.alignment="CENTER" fx:controller="com.kalkulator.snuskalkulator.NavigationController" xmlns="http://javafx.com/javafx"
          xmlns:fx="http://javafx.com/fxml" stylesheets="assets/focused.css">
        <children>
            <Button mnemonicParsing="false" fx:id="profileBtn" onAction="#handleProfileBtn" text="Profil"/>
            <Button mnemonicParsing="false" fx:id="snusBtn" onAction="#handleSnusBtn" text="Snus" />
            <Button mnemonicParsing="false" fx:id="taperBtn" onAction="#handleTaperBtn" text="Nedtrapning" />
            <Button mnemonicParsing="false" fx:id="settingsBtn" onAction="#handleSettingsBtn" text="Innstillinger" />
            <Button mnemonicParsing="false" fx:id="graphBtn" onAction="#handleGraphBtn" text="Graf" />
        </children>
        <BorderPane.margin>
            <Insets />
        </BorderPane.margin>
        <padding>
            <Insets left="20.0" />
        </padding>
    </HBox>

This is my NavigationController:

public class NavigationController {



    @FXML
    Button profileBtn, graphBtn, settingsBtn, taperBtn, snusBtn;

    public void handleSettingsBtn() throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("Innstillinger.fxml"));
        Stage window = (Stage) settingsBtn.getScene().getWindow();
        settingsBtn.setStyle("-fx-background-color: red;");
        window.setScene(new Scene(root, 500, 500));
    }


}

Here I try to change the color of the settingsBtn, but nothing happens. Inside of "Innstillinger.fxml" I I include the fxml of the NavigationBar like this:

<fx:include source="NavigationBar.fxml"/>

I have no clue what the reason for the style not changing is. Any help would be appreciated.