Sub checkdifferences()
Dim LastRevRow As Long
Dim LastAlphaRow As Long
Dim i As Integer
Dim j As Integer
LastRevRow = Sheets("Reversion").Cells(Rows.Count, "B").End(xlUp).Row
LastAlphaRow = Sheets("Alpha").Cells(Rows.Count, "B").End(xlUp).Row
For i = 2 To LastRevRow
  For j = 2 To LastAlphaRow
    If Sheets("Reversion").Cells(i, 2).Value = Sheets("Alpha").Cells(j, 2).Value And Sheets("Reversion").Cells(i, 6).Value <> Sheets("Alpha").Cells(j, 6).Value Then
      Sheets("Alpha").Cells(j, 6).Font.Color = rgbRed
      Sheets("Alpha").Cells(j, 6).Copy Sheets("Reversion").Cells(i, 6)
    End If
  Next j
Next i
End Sub
Will also overwrite data in Revision sheet if corresponding cell in Alpha sheet is blank