property ExContextMenu.FlatBackColor as Color
Specifies the color to left part of the menu.

TypeDescription
Color A Color expression that indicates the control's background color. The last 7 bits in the high significant byte of the color indicates the identifier of the skin being used. Use the Add method to add new skins to the control. If you need to remove the skin appearance from a part of the control you need to reset the last 7 bits in the high significant byte of the color being applied to the background's part.
Use the FlatBackColor property to specify the background color of the left side of the control. This property has effect while the control's MenuAppearance property is exMenuFlat. The BackColor property specifies the control's background color. The ForeColor property specifies the control's foreground color. The SelBackColor property specifies the visual appearance of the item being selected / highlighted. The SelForeColor property specifies the foreground color of the item being selected / highlighted. The Background property specifies the visual appearance for different parts of the control. The Appearance property specifies the menu's frame appearance. The Background(exMenuFlatLineColor) property indicates the color of line that divides the left to right side of the menu, when the MenuAppearance property is exMenuFlat.