<!DOCTYPE html>
<html>
<head>
<style type="text/css">

.select  {
    width: 100px;
    height:100px;
    font-family: sans-serif;
    font-size: 12px;
    border: 1px solid black;
    box-sizing: border-box;
}

.option {
    margin-left: 2px;
    margin-bottom: 1px;
}
.optgroup {
    margin-left: 2px;
    margin-bottom: 1px;
    font-weight: bold
}

#cover {
    position: absolute;
    width: 100px;
    height:300px;
    background-color: black;
    left: 80px;
    top: 0px;
}
.red { color: red; }
</style>
</head>
<body>
<div class=select>
    <div class=option>One</div>
    <div class="option red">Two</div>
</div>
<div class=select>
    <div class=optgroup>Optgroup1</div>
    <div class="optgroup red">Optgroup2</div>
</div>
<div id=cover></div>
</body>
</html>