css/css-values/attr-namespace-valid.xhtml

<!DOCTYPE xhtml>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:color="http://www.example.com/">
<head>
<link rel="help" href="https://drafts.csswg.org/css-values-5/#attr-notation"></link>
<link rel="match" href="../reference/ref-filled-green-100px-square.xht"></link>
    <style>
        @namespace color "http://www.example.com/";

        div {
            background-color: red;
        }

        .a {
            width: 100px;
            height: 100px;
            background-color: attr(color|myAttr type(*), red);
        }
    </style>
</head>
<body>
    <p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
    <div class="a" color:myAttr="green"></div>
</body>
</html>