Disable Vertical scrolling of the main screen.
Now create a VerticalFieldManager with vertical scroll enabled. This will be the main manger where screen component have to add. Set the width and height of this manager as Screen width and height by overriding sublayout() method.
And override paint() method to set backgroung color
Here is the example code with above implemented.
Also have a look at this KnowledgeBase Article for getting better idea.