[SOLVED] Highlight cell if value is present in any cell in another column

I want to highlight the cell in column A if it is repeated anywhere in column B. For example:

A      | B
pack_1 | unrelated
pack_2 | unrelated
pack_3 | pack_1
pack_4 | pack_1
pack_5 | pack_3
pack_6 | pack_3
pack_7 | unrelated
pack_8 | pack_2

In the example, pack_1, pack_2 and pack_3 should be highlighted because they are mentioned in column B.

How can I do such a thing?

Do conditional formatting on each cell with the formula:

=EQ(VLOOKUP(A1, B:B, 1, FALSE), A1)

And format the cell to a different color if it matches.

I shared an example here (this link will ask you to make a copy in your own Google Drive account):