Highlight Duplicates

Sub ColorDuplicates()
'Color duplicate items between Sheet1.columns A and Sheet2.Column A
    For i = 1 To Sheets("Sheet1").Range("A65536").End(xlUp).Row
         If Application.WorksheetFunction.CountIf(Sheets("Sheet2").Range("A:A"), Sheets("Sheet1").Range("A" & i)) = 1 Then
            With Sheets("Sheet1").Range("A" & i).Font
                .ColorIndex = 3
                .Bold = True
            End With
         Else
            With Sheets("Sheet1").Range("A" & i).Font
                .ColorIndex = 1
                .Bold = False
            End With
         End If
    Next i
    For i = 1 To Sheets("Sheet2").Range("A65536").End(xlUp).Row
         If Application.WorksheetFunction.CountIf(Sheets("Sheet1").Range("A:A"), Sheets("Sheet2").Range("A" & i)) = 1 Then
            With Sheets("Sheet2").Range("A" & i).Font
                .ColorIndex = 3
                .Bold = True
            End With
         Else
            With Sheets("Sheet2").Range("A" & i).Font
                .ColorIndex = 1
                .Bold = False
            End With
         End If
    Next i
End Sub

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