今天是个好日子！我目前正在使用CSS和Bootstrap设计登录表单。当我将鼠标对准用户名文本字段时，其边框颜色变为蓝色。我想更改文本框的边框颜色。
码：
<div class="row">
<div class="col-lg-6 col-md-6 col-sm-6 col-xs-6" style="background: #1b4d32;">
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