By default text span text is red, seems odd for that to be the default style.

Using textSpan and flutter run -d chrome --release --dart-define=FLUTTER_WEB_USE_EXPERIMENTAL_CANVAS_TEXT=true

code snippet:

Widget build(BuildContext context) {
    return MaterialApp(
      title: 'text sample',
      home: Scaffold(
        appBar: AppBar(
          title: Text('text sample'),
        ),
        body: Center(
          child: RichText(
            text: TextSpan(text: 'testing testing is this red by default'),
          ),
        ),
      ),
    );

Results:

[✓] Flutter (Channel master, 1.19.0-4.0.pre.81, on Mac OS X 10.15.3 19D76, locale en-US)
• Flutter version 1.19.0-4.0.pre.81 at /Users/mariamhas/Developer/flutter
• Framework revision 5722adf (76 minutes ago), 2020-06-05 12:40:02 -0700
• Engine revision e87a05f
• Dart version 2.9.0 (build 2.9.0-13.0.dev 62903873df)