Add this line after you bind your ListBox:
ListBox1.DataBind();
ListBox1.Visible = true;
if(ListBox1.Items.Count>0)
ListBox1.Items[0].Attributes.Add("style", "background-color:Red;");
or
ListBox1.DataBind();
ListBox1.Visible = true;
if(ListBox1.Items.Count>0)
ListBox1.Items[0].Attributes.Add("style", "color:Red;");