Changege select2 background using jquery
$("#element_id").select2().data("select2").$container.find(".select2-selection,.select2-selection__rendered").css({"background-color":"#337ab7","color":"#FFFFFF"});
$("#element_id").select2().data("select2").$container.find(".select2-selection,.select2-selection__rendered").css({"background-color":"#337ab7","color":"#FFFFFF"});