Sub test()
Dim sh As Worksheet, sh2 As Worksheet, cellule As Range
Set sh = Worksheets("Le fichier de Chloé Old")
Set sh2 = Worksheets("Tampon")
ActiveWorkbook.Names.Add Name:="Actions_Old", RefersToR1C1:=sh.Range("C3", [C65000].End(xlUp))
Set plage3 = sh2.Range("B3", [B65000].End(xlUp))
For Each cellule In plage3.Cells
With Application
cellule.Interior.ColorIndex = .IfError(.VLookup(cellule.Value, [Actions_Old], 1, False), 6, 3)
End With
Next ValCellule
ActiveWorkbook.Names("Actions_Old").Delete
End Sub