How about
Code:
Private Sub Workbook_Open()
   Dim Cl As Range
   Dim x As Long
   With Sheets("Sheet1")
      For Each Cl In .Range("I1", .Range("I" & Rows.Count).End(xlUp))
         x = InStr(1, Cl, "ERROR", vbTextCompare)
         If x > 0 Then
            Cl.Font.ColorIndex = xlAutomatic
            Cl.Characters(x, 5).Font.Color = vbRed
         End If
      Next Cl
   End With
End Sub