为何图标在输入框下面，颜色还是默认的黑色

Question

<div class="form-group has-error has-feedback">  <label class="control-label" for="inputError2">Input with error</label>  <input type="text" class="form-control" id="inputError2" >  <span class="glyphicon glyphicon-remove form-control-feedback" ></span></div>