Flagging Values in Column that don't match values in separate sheet

Hello,

I was wondering if it would be possible to flag values in a column that do not match values in a separate sheet. I tried modifying a Macro code that I found online, but I was largely unsuccessful.

But, the gist of what I am trying to do is to scan a column (e.g. Column G in Sheet 1), and flag any values that are not in a column on the next sheet (e.g. Column A of Sheet 2)

Is there a quick and easy code that could accomplish this?

Thanks in advance for all of the help.