<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<!-- import CSS -->
<link rel="stylesheet" href="https://unpkg.com/element-ui/lib/theme-chalk/index.css">
</head>
<style>
.el-tooltip__popper[x-placement^=bottom] .popper__arrow{
border-bottom-color: red;
}
.el-tooltip__popper[x-placement^=bottom] .popper__arrow:after {
border-bottom-color: red;
}
.test{
background: red !important;
}
</style>
<body>
<div id="app">
<el-tooltip content="Top center" placement="bottom" popper-class="test">
<el-button>Dark</el-button>
</el-tooltip>
</div>
</body>
</html>
引入相应的vue.js和element-ui/lib/index.js