Cesium color

dojo.xhrGet({
    url: filePath,
    load: function(result){
        var jsonResult = JSON.parse(result);
        var color;
        var width;
        for(var i in jsonResult){
            if(jsonResult[i].event_type == "speeding_down"){
                color = new Cesium.Color(1.0, 1.5, 0.0, 1.0);
                width = 1;
            }else if(jsonResult[i].event_type == "speeding_up"){
                color = new Cesium.Color(1.0, 2.5, 0.0, 1.0);
                width=5;
            }else{
                color = new Cesium.Color(1.0, 0.5, 0.0, 1.0)
                width=8;
            }

            polylines.add({
                positions:ellipsoid.cartographicArrayToCartesianArray([
    new Cesium.Cartographic.fromDegrees(jsonResult[i].startpointx, jsonResult[i].startpointy),
    new Cesium.Cartographic.fromDegrees(jsonResult[i].endpointx, jsonResult[i].endpointy)
                ]),
                width:width,
                "material.uniforms.color" : color
            });
        }
     },
    changeURL: true,
    mimetype: "text/plain"
});