Incrémentation couleur

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim Cell As Range
    Range("A65536").End(xlUp).Select
    derligne = ActiveCell.Row
    Set Plg = Range([A1], [A65536].End(xlUp))
    For Each Cell In Plg
        For a = 0 To derligne Step 10
            If Cell.Value = a + 1 Then Cell.Interior.ColorIndex = 27
        Next a
        For b = 0 To derligne Step 10
            If Cell.Value = b + 2 Then Cell.Interior.ColorIndex = 3
        Next b
        For c = 0 To derligne Step 10
            If Cell.Value = c + 3 Then Cell.Interior.ColorIndex = 4
        Next c
    Next Cell
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
    Select Case Right(Target.Value, 1)
    Case 0
        Target.Interior.ColorIndex = 15
    Case 1
        Target.Interior.ColorIndex = 27
    Case 2
        Target.Interior.ColorIndex = 3
    Case 3
        Target.Interior.ColorIndex = 4
    Case 4
        Target.Interior.ColorIndex = 8
    Case 5
        Target.Interior.ColorIndex = 21
    Case 6
        Target.Interior.ColorIndex = 55
    Case 7
        Target.Interior.ColorIndex = 1
    Case 8
        Target.Interior.ColorIndex = 46
    Case 9
        Target.Interior.ColorIndex = 7
    End Select
End Sub