I have screen with scrollview wich expands little bit after user actions and it doesnt fill all screen height, the thing i want to do is to change this bottom line color, how to do this?

<ScrollView
        android:id="@+id/scroll"
        android:layout_width="0dp"
        android:layout_height="56dp"
        app:layout_constrainedHeight="true"
        app:layout_constraintBottom_toTopOf="@id/footer"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@id/appBar"
        app:layout_constraintVertical_bias="0.0">

           ...

    </ScrollView>

im talking about this line
bottom line

i tried changing background but it doesnt affect this line