Change Shape color with MouseMoveEvent

Dear All
I’ve design a shape using png image and all is ok (i see on map in defined lat/lng position). Now I like to move mouse over the shape and I like to change color, but no action. Mycode is:

    ' it's assumed here that the layer we want to edit is the first 1 (with 0 index)
    Dim sf As New Shapefile
    sf = AxMap.get_Shapefile(m_layerTower)
    If sf IsNot Nothing Then
        Dim projX = 0.0
        Dim projY = 0.0
        AxMap.PixelToProj(e.y, e.x, projX, projY)
        'AxMap.DegreesToProj(11.9, 44.4, projX, projY)

        Dim result As Object = Nothing
            Dim ext = New Extents()
            ext.SetBounds(projX, projY, 0.0, projX, projY, 0.0)
        If sf.SelectShapes(ext, 2000, SelectMode.INTERSECTION, result) Then
            Dim shapes As Integer() = TryCast(result, Integer())
            If shapes IsNot Nothing AndAlso shapes.Length = 1 Then
                Dim ut As New Utils

                sf.SelectionAppearance = tkSelectionAppearance.saDrawingOptions
                sf.SelectionDrawingOptions.PointSize = sf.DefaultDrawingOptions.PointSize
                sf.SelectionDrawingOptions.PointRotation = sf.DefaultDrawingOptions.PointRotation
                sf.SelectionDrawingOptions.PointShape = sf.DefaultDrawingOptions.PointShape
                sf.SelectionAppearance = tkSelectionAppearance.saSelectionColor
                sf.SelectionColor = ut.ColorByName(tkMapColor.Red)
            End If
        End If
    End If

In fact the mouse position close to shape is recognized, but seems no action to change color.

Can someone else help me ?

Thanks , Daniele