Краткий ответ :
Text(
"Hello World",
style: TextStyle(backgroundColor: Colors.blue), // give any color here
)
Полный ответ
Вы можете использовать это в своем showDialog
вызове, вот полный виджет, который вы искали.
Dialog(
elevation: 12,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
mainAxisSize: MainAxisSize.min,
children: <Widget>[
Container(
color: Colors.blue[800],
width: double.maxFinite,
alignment: Alignment.center,
padding: EdgeInsets.symmetric(vertical: 16),
child: Text(
"Your Profile...",
style: TextStyle(fontSize: 20, color: Colors.white),
),
),
Padding(
padding: EdgeInsets.symmetric(horizontal: 32),
child: Column(
children: <Widget>[
SizedBox(height: 12),
TextField(decoration: InputDecoration(hintText: "Select a Photo")),
TextField(decoration: InputDecoration(hintText: "Take a Photo...")),
TextField(decoration: InputDecoration(hintText: "Choose form Library")),
],
),
),
Container(
padding: EdgeInsets.symmetric(vertical: 12),
child: RaisedButton(
shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(50)),
child: Text("Back"),
onPressed: () {},
color: Colors.red,
textColor: Colors.white,
),
)
],
),