I have a row with only flexible expanded widgets:

Row(child:[
   Expanded(flex:1, child: greenChild),  //Expanded -> Flexible, same result
   Expanded(flex:3, child: redChild),
]);

What I see is:
… the green child is black (not green) — it is actually unpainted and changes from white/black when dragging the window between desktops (This is a linux target).
Why is this? How can I fix it?

void main() {
  Widget child = Row(
    children: [
      Expanded(
        flex: 1,
        child: Expanded(
            child: Container(
                color: Colors.green, child: Container(color: Colors.yellow))),
      ),
      Expanded(
          flex: 3,
          child: Container(
            color: Colors.red,
          )),
    ],
  );

  return runApp(MaterialApp(
      debugShowCheckedModeBanner: false,

      // Does not help
      home: Scaffold(
        body: Builder(builder: (context) => child),
      )));
}

The Widget inspector shows that the left column data has a defined size:

If I remove red container, I get the result below (yellow container). Why is this not a fixed size? Is this related to the first problem?

  Widget child = Row(
    children: [
      Expanded(
        flex: 1,
        child: Container(
            color: Colors.green,
            child: Container(width: 50, height: 50, color: Colors.yellow)
        ),
      ),
      // Expanded(
      //     flex: 3,
      //     child: Container(
      //       color: Colors.red,
      //     )),
    ],
  );