Highlight duplicate columns

Generic formula 

=SUMPRODUCT((row1=ref1)*(row2=ref2)*(row3=ref3))>1

Summary 

Excel contains a built-in preset for highlighting duplicate values with conditional formatting, but it only works at the cell level. If you want to find and highlight duplicate columns, you'll need to use your own formula, as explained below.

To highlight duplicate columns, you can use a formula based on the SUMPRODUCT function. In the example shown, the formula used to highlight duplicate columns is:

=SUMPRODUCT(($B$4:$E$4=B$4)*($B$5:$E$5=B$5)*($B$6:$E$6=B$6))>1

How to use SUMIFS with an Excel Table

Explanation 

This approach uses SUMPRODUCT to count the occurrence of every value in the table, one row at a time. Only when the same value appears in the same location in all three rows is a count generated. For cell B4, the formula is solved like this:

=SUMPRODUCT(($B$4:$E$4=B$4)*($B$5:$E$5=B$5)*($B$6:$E$6=B$6))>1
=SUMPRODUCT(({1,1,1,1})*({1,0,1,0})*({1,0,1,0}))>1
=SUMPRODUCT({1,0,1,0})>1
=2>1
=TRUE