// Repeater
<asp:Repeater ID="SidebarRepeater" runat="server" onitemdatabound="SidebarRepeater_ItemDataBound">
    <ItemTemplate>
        <a id="A1" href='<%# Eval("Url") %>' runat="server">
                    <span><%# Eval("Name") %></span>
                </a>
    </ItemTemplate>
 </asp:Repeater>

// Event
        protected void SidebarRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
        {
            if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
            {
                HtmlAnchor a = (HtmlAnchor)e.Item.FindControl("A1");
                a.Attributes.Add("style", "background-color: " + NEED DATA HERE +";");
            }
        }

// Datasource item
    public class MenuItem
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public string Url { get; set; }
        public string ImageRef { get; set; }
    }

// The datasource is a List<MenuItem> and works fine on the page.
//