点击当前选中可多选

$(function(){
                $(".project li").toggle(function(){

                    $(this).css({"backgroundColor":"#00c5b5","color":"#fff"});

                    $(this).children("span").css("display","inline-block");

                },function(){

                    $(this).css({"backgroundColor":"#fff","color":"#000"});
                    
                    $(this).children("span").css("display","none");
                });
            })

<ol class="project cleafix">
							<li><span></span>牙齿矫正</li>
							<li><span></span>牙齿种植</li>
							<li><span></span>牙齿修复</li>
							<li><span></span>牙齿美白</li>
							<li><span></span>超薄贴面</li>
							<li><span></span>儿牙齿科</li>
						</ol>