var formen = [{
    "type": "Feature",
    "properties": {
        "farbe": "red",
        "info": "BT 56"
    },
    "geometry": {
        "type": "Polygon",
        "coordinates": [[
        	[ 8.896696195006372, 53.054442380171004], //Reihenfolge umgekehrt: LonLat
        	[ 8.896603155881166, 53.05449229656882],
        	[ 8.896517828106882, 53.054433855886636],
			[ 8.89661053195596 , 53.05438418124448]
       	]]
    }
}

];

L.geoJson(formen,{
    style: function(feature){
		return {weight: 1, color: feature.properties.farbe};
	},
    onEachFeature: onEachFeature
 } 
).addTo(map);

function onEachFeature(feature, layer) {
    if (feature.properties && feature.properties.info) {
        layer.bindPopup(feature.properties.info);
    }
}