<!DOCTYPE html>

<html>
<head>
    <style>
        .masked {
            height: 100px;
            width: 100px;
            background-color: green;
            -webkit-mask-image: url(data:image/png;base64,R0lGODlhAQABAIAAAP///////yH5BAEKAAEALAAAAAABAAEAAAICRAEAOw==);
        }
    </style>
</head>
<body>
    <div class="masked"></div>
</body>
</html>