Container(
    width: double.infinity,
    margin: EdgeInsets.symmetric(horizontal: 15.0),
    child: RaisedButton(
    onPressed: () {
    },
    padding: EdgeInsets.all(20),
    color: Colors.grey[600],
    textColor: Colors.white,
    child: Text('Klicka här', style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold)),
    ),
),

Container(
    width: double.infinity,
    margin: EdgeInsets.symmetric(horizontal: 15.0),
    child: RaisedButton(
    elevation: 0,
    onPressed: () {
    },
    padding: EdgeInsets.all(20),
    color: Colors.red[800],
    textColor: Colors.white,
    child: Text('Klicka här', style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold)),
    shape: StadiumBorder()
    ),
),