<div class="border"></div>

.border {
	max-width: 300px;
	width: 100px;
	height: 100px;
	
	border-top: 10px solid #f44;
	border-bottom: 10px solid #4f4;
	border-left: 10px solid #333;
	border-right: 10px solid #44f;
}

html,body {
	height: 100%;
	display: grid;
	place-content: center;
}