olor = CLR_INVALID
    End If
End Function

''' &lt;summary&gt;
''' Blends two colours together using the specified alpha amount.
''' &lt;/summary&gt;
''' &lt;param name="oColorFrom"&gt;Base Colour.&lt;/param&gt;
''' &lt;param name="oColorTo"&gt;Colour to blend.&lt;/param&gt;
''' &lt;param name="alpha"&gt;Amount of alpha (0-255) to use in the blend.&lt;/param&gt;
''' &lt;returns&gt;Blended colour as RGB&lt;/returns&gt;
Public Property Get BlendColor( _
      ByVal oColorFrom As OLE_COLOR, _
      ByVal oCol