Help with getting two cells to match based on cell color and adjacent cells

Let me start by saying I am far from an Excel expert so please dumb it down for me...

I am trying to find a quick way to get two cells that are different in column A to match based on cell background color, if the data in column be that is adjacent is duplicated.

Best way to describe it is to show you a screenshot...

If the data in column B is duplicate, then I want the number in column A next to it, that is highlighted yellow to copy to the other cell that matches the duplicate cell in column B.  How do I do that?  I don't want to go through this manually... there are over 3000 rows.