//html dropdownlistSelect1.Items.Add("1");Select1.Items.Add("2");Select1.Items.Add("3");Select1.Items.Add("4");Select1.Items[1].Attributes.CssStyle.Add("BACKGROUND-COLOR","green");Select1.Items[3].Attributes.CssStyle.Add("COLOR","red");//to execute onchange event on selected index chage [auto postback]Select1.Attributes.Add("onchange","__doPostBack('Select1','')");//web control dropdownlistDropDownList1.Items.Add("0");DropDownList1.Items.Add("1");DropDownList1.Items.Add("2");DropDownList1.Items.Add("3");DropDownList1.Items.Add("4");DropDownList1.Items[2].Attributes.CssStyle.Add("BACKGROUND-COLOR","green");DropDownList1.Items[4].Attributes.CssStyle.Add("COLOR","red");//This will not reflect..No color will be set for a particular item.