Sub Gourdin()
Dim i As Long, AColorer As Boolean
AColorer = True
With Worksheets("Feuil1") ' à adapter
For i = 3 To .Range("B" & Rows.Count).End(xlUp).Row
If AColorer = True Then .Cells(i, 2).Resize(1, 3).Interior.ColorIndex = 6
If Not (.Cells(i, 2) = .Cells(i + 1, 2) And .Cells(i, 3) = .Cells(i + 1, 3)) Then AColorer = Not AColorer
Next
End With
End Sub