Highlighting/Changing the cell color for multiple cells in a column

Hey again everyone. I'm working with a huge database now that includes in each row one column that lists phone numbers. I want to be able to highlight when multiple rows have the same phone number. I can sort them so that they'll be assembled together on the database, but trying to look through about 9000 rows makes me go crosseyed eventually. I was hoping there's a way to get excel to simply change the color of the cell (or alternate highlighting and not) when the phone number changes.

So for example:

Steve 555-1212
Barry 555-7000
Martin 555-7000
Clara 555-1345
Emily 555-1345
Sandra 555-6754
Pete 555-7890

Something along those lines, only with the cell color changing, not the text, so it's easily identifiable which numbers are the same going down the list (which appear to either be duplicates or the same number for multiple rows) and a way to identify when the numbers change at a glance.

Is this doable?