openlayers 4.4：更改wms源的颜色和符号

Question

这是一个wms源（地图服务器），我想更改其颜色和符号。请问该怎么办？

var installationsClasseesSourceWms =   new ol.layer.Tile({
        title: 'carte geol',
        visible: false,
        //opacity: 0.0,
        source: new ol.source.TileWMS({
          url: 'http://mapsrefrec.brgm.fr/wxs/georisques/georisques_services?',
          params: {LAYERS: 'INSTALLATIONS_CLASSEES_SIMPLIFIE_GE', TILED: true,  FORMAT: 'image/png'},
          extent: [40428,1600797,1216896,2698833.8],
          resolutions: [1056.633663,528.3168317,264.1584158,132.0792079,66.03960396,26.41584158, 13.229166668, 6.614583334, 2.645833334],
        projection:"EPSG:4326",
                 transitionEffect: 'resize',
                 //isBaseLayer:true,
                 reproject: true,
                 //opacity: 0.0
        }),
          });
map.addLayer(installationsClasseesSourceWms);