a System.Drawing.Color
Use the Style.BackColor property to specify the background color of the Web server control. This property is set using a System.Drawing.Color object.
This property will render only for certain controls. For example, System.Web.UI.WebControls.Table, System.Web.UI.WebControls.Panel, System.Web.UI.WebControls.DataGrid, System.Web.UI.WebControls.Calendar, and System.Web.UI.WebControls.ValidationSummary will render this property. It will also work for System.Web.UI.WebControls.CheckBoxList, System.Web.UI.WebControls.RadioButtonList and System.Web.UI.WebControls.DataList if their RepeatLayout property is RepeatLayout.Table, and not RepeatLayout.Flow.
In general, only controls that render as a <table> tag can display a background color in HTML 3.2, whereas almost any control can in HTML 4.0.
For controls that render as a <span> tag (including System.Web.UI.WebControls.Label, all validation controls, and list controls with their RepeatLayout property set to RepeatLayout.Flow), this property will work in Microsoft Internet Explorer version 5 or later, but not for Microsoft Internet Explorer version 4.