Свойство border-top-style

border-top-style: none | hidden | dotted | dashed | solid | double | groove | ridge | inset | outset;

<!DOCTYPE html>
<html lang='ru'>
<head>
<meta charset='UTF-8'>
<meta name='viewport' content='width=device-width, initial-scale=1.0'>
<title>Document</title>
</head>
<body>
<style>
#test1 {
width: 300px;
height: 200px;
border: 10px rgb(208, 255, 0);
background-color: rgba(32, 92, 144, 0.416);
border-top-style: double;
}
</style>
<div id='test1'></div>
</body>
</html>