title: Draggable div background to be one colour when over div1 and then another when over div2
body: <p>I have a draggable div which is initially positioned over a blue header so has a white background with blue text and white border so it stands out.
  When it is dragged over the rest of the page which has a white background I would like the background to become blue, text white and border blue.</p>
  
  <p>The draggable div is positioned using absolute so is actually placed outside of the header element so it would need to detect what area of the page it is over.</p>
  
  <p>Can this be done using CSS or Javascript / jQuery? </p>