The default CSS theme (kanban_default) is built-in (it doesn't require an additional CSS stylesheet to be loaded).
Creating Custom Themes
You can create a custom theme by modifying the default theme. Save it to a new .css file and link this file in the HTML page.
The online CSS theme designer will support Kanban themes in the near future.
JavaScript
You can specify a custom CSS theme using theme property:
<!DOCTYPE html>
<html>
<head>
<!-- ... ->
<link type="text/css" rel="stylesheet" href="my_kanban_theme.css" />
</head>
<body>
<div id="dp"></div>
<script type="text/javascript">
var dp = new DayPilot.Kanban("dp");
// ...
dp.theme = "my_kanban_theme";
dp.init();
</script>
</body>
</html>
DayPilot