您可以通过如下更改主题primaryColor来更改TabBar的颜色：

return MaterialApp(
      theme: ThemeData(
        brightness: Brightness.light,
        primaryColor: Colors.pink[800], //Changing this will change the color of the TabBar
        accentColor: Colors.cyan[600],
      ),
      home: DefaultTabController(
        length: 3,
        child: Scaffold(
          appBar: AppBar(
            bottom: TabBar(
              indicatorColor: Colors.lime,
              tabs: [
                Tab(icon: Icon(Icons.directions_car)),
                Tab(icon: Icon(Icons.directions_transit)),
                Tab(icon: Icon(Icons.directions_bike)),
              ],
            ),
            title: Text('Tabs Demo'),
          ),
          body: TabBarView(
            children: [
              Icon(Icons.directions_car),
              Icon(Icons.directions_transit),
              Icon(Icons.directions_bike),
            ],
          ),
        ),
      ),
    );

如果您不在AppBar中使用它，则可以将TabBar包裹在Material小部件中并设置color属性，如下所示：

class TabBarDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Tabs Demo'),
        ),
        body: DefaultTabController(
          length: 3,
          child: Column(
            children: <Widget>[
              Container(
                constraints: BoxConstraints(maxHeight: 150.0),
                child: Material(
                  color: Colors.indigo,
                  child: TabBar(
                    tabs: [
                      Tab(icon: Icon(Icons.directions_car)),
                      Tab(icon: Icon(Icons.directions_transit)),
                      Tab(icon: Icon(Icons.directions_bike)),
                    ],
                  ),
                ),
              ),
              Expanded(
                child: TabBarView(
                  children: [
                    Icon(Icons.directions_car),
                    Icon(Icons.directions_transit),
                    Icon(Icons.directions_bike),
                  ],
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}