在App.xaml.cs中，设置应用程序根框架的background属性.您可以在导航到初始页面之前，使用覆盖的OnLaunch方法进行操作.

In App.xaml.cs, set the background property of the app's root frame. You can do it in the overridden OnLaunch method, just before navigation to the initial page.

rootFrame.Background =新的SolidColorBrush(Colors.White); //什么颜色

rootFrame.Background = new SolidColorBrush(Colors.White); //whatever color