Flutter – Changing the border color of the OutlineInputBorder

Since July you can now use enabledBorder:

new TextField(
  decoration: new InputDecoration(
    enabledBorder: const OutlineInputBorder(
      // width: 0.0 produces a thin "hairline" border
      borderSide: const BorderSide(color: Colors.grey, width: 0.0),
    ),
    border: const OutlineInputBorder(),
    labelStyle: new TextStyle(color: Colors.green),
    ...
  ),
)

See the full documentation for the new decorators