Sub Worksheet_Change(ByVal Target As Range)
If Target.Count > 1 Then Exit Sub
If Not Intersect(Target, [C1]) Is Nothing Then
With ActiveSheet.Shapes("Triangle isocèle 1")
If Target = "" Then
.Fill.ForeColor.RGB = vbRed
Else
.Fill.ForeColor.RGB = vbGreen
End If
End With
End If
End Sub