Help Getting Cells I Need

Hey,

What I want to do is compare values from column A and B, and select only the unique values that are found in column A. To do this, I select both columns, and conditionally format them to highlight unique values. Once done, all all unique values that I am interested in are highlighted red in column A.

From here, I would either sort, or filter by cell color in column A so that all red cells (the ones I want) would be grouped together and from there I can easily copy and paste them. Unfortunately, I can no longer do this as there is too many rows of data (over 500,000) and both the sort and filter feature take 16+ hours to sort/filter based on color (and I am running a deca-core server w/ 64 gb of ram). So of course, this takes far too long, and I can't even use my computer while this sort is running because even a mouse click makes excel crash at this point.

So, my question is, is there another way to select only these red cells without sorting them? I have tried to select cells based on format, however for whatever reason, formats applied by conditional formatting are not recognized when using the find & select feature, so this doesn't work either? Anyone have a solution? Thanks.