highlight color of duplicate numbers
 

I am using a vlook instead of the count if formula to bring a duplicate
number from one worksheet to another. I am using the same formula to bring
in the duplicate number in worksheet 1 from worksheet 2 and worksheet 2 to
worksheet 1. This way I can see the duplicate numbers on both worksheets.
I have over 18,000 rows of infor. Question: is there a way to color code
the number in worksheet 1 where the duplicate number is found to be the same
as in the worksheet 2 cell? This way I can look at the number highlighted
example as yellow on worksheet 1 and then go to worksheet 2 and see the same
number quickly because it is highlighted yellow and the next matching numbers
maybe highlighted in blue, etc.
Thanks,