remove blue background from markers

how to remove the blue background from the markers?
this happen using default icon and a custom one (png with transparent background)

am I doing something wrong?

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@picocss/pico@1/css/pico.min.css">
    <link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/leaflet.css" />
    <title>Map with OpenStreetMap</title>
    <style>
        #map {
            height: 400px;
        }
    </style>
</head>
<body>
    <div id="map"></div>
    <script src="https://unpkg.com/[email protected]/dist/leaflet.js"></script>
    <script>
        var map = L.map('map').setView([45.418393, 10.969487], 13); // Replace with your default map center

        L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
            maxZoom: 19,
            attribution: '© OpenStreetMap contributors'
        }).addTo(map);

        var marker = L.marker([45.410051797705904, 10.90330758434609]).addTo(map);

    </script>
</body>
</html>

enter image description here

tried with a custom icon but still got the same problem

var LogoPin = L.icon({
    backgroundColor: 'transparent',
    iconUrl: './pin.png',
    shadowUrl: './shad.png',
    iconSize:     [30, 47], // size of the icon [38,95]
    shadowSize:   [50, 64], // size of the shadow*/
    iconAnchor:   [22, 94], // point of the icon which will correspond to marker's location
    shadowAnchor: [4, 62],  // the same for the shadow*/
    popupAnchor:  [-3, -76] // point from which the popup should open relative to the iconAnchor
    
});

L.marker([place.lat, place.lng], {icon: LogoPin}).addTo(map);