whmcsCrosterTemplates/core/includes/theme-header.tpl

<style rel="stylesheet">
.theme-colors {
	position: fixed;
	right: 15px;
	bottom: 0;
	margin-bottom: 90px;
	width: 290px;
	z-index: 5000;
	background-color: #fff;
	border: 1px solid #ccc;
	box-shadow: 0px 4px 6px 0px rgba(0, 11, 40, 0.1);
	padding: 0 15px 15px;
	border-radius: 4px;
}
.theme-colors-container {
	max-height:390px;
	overflow-y: auto;
	overflow-x: hidden;
}
.swal-footer {
	text-align: center;
}
</style>

<script>
	less = {
		javascriptEnabled: true
	};
</script>
<script src="{$WEB_ROOT}/templates/{$template}/assets/js/less.min.js"></script>