Flutter webview scaffold

My flutter web-view scaffold URL is working but the default color of the web page is not working.
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```import 'package:flutter/material.dart';
import 'package:flutter_webview_plugin/flutter_webview_plugin.dart';
import 'package:system_shortcuts/system_shortcuts.dart';
import 'package:splashscreen/splashscreen.dart';
import 'package:flutter/rendering.dart';

void main() => runApp(MaterialApp(
home: MyApp(),
debugShowCheckedModeBanner: false,
theme: ThemeData(
primaryColor: Colors.blueGrey[900],
brightness:Brightness.light,
fontFamily: 'Bungee',
primaryTextTheme: TextTheme(
title: TextStyle(color: Colors.yellow),
),
)));

class MyApp extends StatefulWidget {
@override
_MyAppState createState() => new _MyAppState();
}

class _MyAppState extends State {
@override
Widget build(BuildContext context) {
return new SplashScreen(
seconds: 2,
navigateAfterSeconds: AfterSplash(),
image: new Image.asset(
'assets/images/icon.png',
width: 100,
height: 100,
),
backgroundColor: Colors.blueGrey[800],
photoSize: 100.0,
loaderColor: Colors.yellow[300],
);
}
}

class AfterSplash extends StatefulWidget {
@override
_MyAppsState createState() => _MyAppsState();
}

class _MyAppsState extends State {
@override
Widget build(BuildContext context) {
return WebviewScaffold(
appBar: AppBar(title: Text("Crypto Signals"),
actions: [
// action button
IconButton(
icon: Icon(Icons.screen_rotation),
onPressed: () async {
await SystemShortcuts.orientLandscape();

}),
]),
url: "http://crypto.slamtrade.com/",
withJavascript: true,
withZoom: true,
withLocalStorage: true,
enableAppScheme: true,
hidden: true,
userAgent: 'https://accounts.google.com/signin/oauth/oauthchooseaccount?client_id=966276189940-1k54igc67tmva1i1tbodfmt3k5kf3e1i.apps.googleusercontent.com&as=bZHn1GRLkEC4_cjzG36PNg&destination=https%3A%2F%2Fslamtrade-ui.firebaseapp.com&approval_state=!ChRHRkRjRUhfeFhDZFMtM3ZQNzZychIfMDZJb0UtTWF2bE1ROEhuU1JuY2dubXFPaVNZSWpoWQ%E2%88%99AJDr988AAAAAXGPAtfiv-BKiA0Kd25fHIHc156Jb1sJX&oauthgdpr=1&xsrfsig=ChkAeAh8TyMGfEj66DNTFSmu0TeDs_vg-UHBEg5hcHByb3ZhbF9zdGF0ZRILZGVzdGluYXRpb24SBXNvYWN1Eg9vYXV0aHJpc2t5c2NvcGU&flowName=GeneralOAuthFlow',
);
}
}