add colors in box decroation flutter code example

Example 1: background color to container flutter

new Container(
  width: 100,
  height: 30,
  decoration: new BoxDecoration(
    color: Colors.green
  ),
 )

Example 2: box decoration s flutter

new Center(  child: new Container(    decoration: new BoxDecoration(      color: Colors.purple,      gradient: new LinearGradient(        colors: [Colors.red, Colors.cyan],        begin: Alignment.centerRight,        end: new Alignment(-1.0, -1.0)      ),    ),    child: new FlutterLogo(      size: 200.0,    )  ),);