The effect of setting an alpha-component on the BackgroundColor while specifying a separate AlphaLevel for the Legend box background fill is undefined. It is recommended that the fill color assigned to Background color always be fully opaque (with an Alpha value of 255) and that any transparency should be added through the AlphaLevel property.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2