Find duplicate values in two columns

Generic formula 

=AND(COUNTIF(range1,A1),COUNTIF(range2,A1))

Summary 

To highlight duplicate values in two or more columns, you can use conditional formatting with on a formula based on the COUNTIF and AND functions.

In the example shown, the formula used to highlight duplicate values is:

=AND(COUNTIF(range1,B5),COUNTIF(range2,B5))