how to change the selected color of listbox in asp.net

[jeannemonkey]

\[code\]<asp:ListBox ID="ddlPA" ClientIDMode="Static" runat="server" AutoPostBack="true" SkinID="x" CssClass="ListBoxCssClass" SelectionMode="Multiple" OnSelectedIndexChanged="ddlPA_SelectedIndexChanged"></asp:ListBox>\[/code\]When i select an item in asp:listbox , the selected item color changes to gray, i want to change the color to blue. how can i do the same?