Replace text in certain color

Try this one, see if I've got it now:

Sub ChangeRed()
Dim i As Integer
Dim x As Range

Application.ScreenUpdating = False
For Each x In Range("C2:C2001")
    For i = Len(x.Value) To 1 Step -1
        If x.Characters(i, 1).Font.Color = vbRed Then
            If x.Characters(i, 1).Text = " " Then
                x.Characters(i, 1).Font.Color = vbBlack
            ElseIf x.Characters(i, 4).Text = x.Characters(i, 1).Text & "ABC" Then
                x.Characters(i, 1).Delete
            Else
                x.Characters(i, 1).Font.Color = vbBlack
                x.Characters(i, 1).Text = "ABC"
            End If
        End If
    Next i
Next x
Application.ScreenUpdating = True
End Sub