Cambio Colore in base a gruppi di valori

Option Explicit
Sub Colore()
    Dim Nriga  As Long
    Dim IColore As Long
    Dim primo  As Variant
    Dim secondo As Variant
    Application.ScreenUpdating = False
    Nriga = 6
    IColore = 19
    Range(Cells(Nriga, 1), Cells(Nriga, 6)).Interior.ColorIndex = IColore
    Do While Cells(Nriga, 1) <> ""
        primo = Cells(Nriga, 1).Value
        secondo = Cells(Nriga, 1).Offset(1, 0).Value
        If secondo = primo Then
            Range(Cells(Nriga, 1), Cells(Nriga, 6)).Interior.ColorIndex = IColore
        Else
            Range(Cells(Nriga, 1), Cells(Nriga, 6)).Interior.ColorIndex = IColore
            If IColore = 20 Then IColore = 19 Else IColore = 20
        End If
        Nriga = Nriga + 1
    Loop
    Application.ScreenUpdating = True
End Sub