property RadialMenu.SubItemsBackAlpha as Byte
Specifies the value of alpha / opacity channel to show the sub items zone of the radial menu.

TypeDescription
Byte A BYTE expression that specifies the value of alpha / opacity channel to show the sub-items portion of the radial menu. 255 indicates opaque, 128 semi-transparent, and 0 fully transparent.
By default, The SubItemsBackAlpha property is 255.  The SubItemsBackColor / SubItemsBackAlpha property specifies the color to show the sub- items zone of the radial menu. The SubItemsSize property specifies the size to display the sub-items zone. The ItemsBackColor / ItemsBackAlpha property Specifies the color to show the items portion of the radial menu. The BackColor property specifies the control's background color. The ParentBackColor / ParentBackAlpha property specifies the color / transparency to show the parent portion of the radial menu. The ParentSize property specifies the size to display the parent zone.  The RadialLineColor(exRadialSubItemsBorder) property specifies the color to show the border around the sub-items section of the control. The RadialLineColor(exRadialSubItemsGridLines) property specifies the color to show the grid lines, inside the sub-items section of the control.