container flutter background color code example

Example 1: background color to container flutter

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

Example 2: how to set opacity of background color in flutter

Opacity(
          opacity: 0.5,
          child: Container(
          color: Colors.red,
          width: 200,
          height: 200,
  ),
        ),