CSS3 为什么 input[type=text] 的左边框和上边框显示为黑色?

CSS3 Why input[type=text]'s border left and top are showing black?

我的问题很简单。怎么把border left和top设置成我想要的颜色?

input.comment-input {
  width: 60%;
  border-color: #2bb6c1;
  border-width: 1px;
}

input.comment-input,
button.btn-comment {
  font-size: inherit;
  padding: 0.2em;
  margin: 0.1em 0.2em;
  -moz-box-sizing: content-box;
  -webkit-box-sizing: content-box;
  box-sizing: content-box;
}

button.btn-comment {
  width: 50px;
  text-align: center;
  color: #2bb6c1;
  background-color: #fff;
  border: dashed 1px #2bb6c1;
  font-size: inherit;
}
<input type="text" class="comment-input">
<button type="button" class="btn-comment">input</button>

这是Js-Fiddle

为此使用 border-leftborder-top 属性

border-left:1px solid red; //set you want color
border-top:1px solid red;  //set you want color

input.comment-input {
  width: 60%;
  border-color: #2bb6c1;
  border-width: 1px;
  border-left: 1px solid red;
  border-top: 1px solid red;
}

input.comment-input,
button.btn-comment {
  font-size: inherit;
  padding: 0.2em;
  margin: 0.1em 0.2em;
  -moz-box-sizing: content-box;
  -webkit-box-sizing: content-box;
  box-sizing: content-box;
}

button.btn-comment {
  width: 50px;
  text-align: center;
  color: #2bb6c1;
  background-color: #fff;
  border: dashed 1px #2bb6c1;
  font-size: inherit;
}
<input type="text" class="comment-input">
<button type="button" class="btn-comment">input</button>

你失踪了吗border-style

   input.comment-input {
   width: 60%;
   border-color: #2bb6c1;
   border-width: 1px;
   /*border-style*/
   border-style: dashed
}