The stuff I tried:

1. Wrapping the entire **NavigationRail** widget with **Theme** widget and passing in **ThemeData** where `splashColor`, `highlightColor`, `hoverColor`, `hintColor` all were set to `Colors.transparent`.

Although this does seem to take away the initial "splash", but the "ripple" effect is still prevalent (specially **onLongPress**).

```
       Theme(
            data : ThemeData(
              splashColor: Colors.transparent,
              highlightColor: Colors.transparent
            ),
            child: NavigationRail(
              selectedIndex: _selectedIndex,
              onDestinationSelected: (int index) {
                setState(() {
                  _selectedIndex = index;
                });
              },
              labelType: NavigationRailLabelType.selected,
              destinations: [
                NavigationRailDestination(
                  icon: Icon(Icons.favorite_border),
                  selectedIcon: Icon(Icons.favorite),
                  label: Text('First'),
                ),
                NavigationRailDestination(
                  icon: Icon(Icons.bookmark_border),
                  selectedIcon: Icon(Icons.book),
                  label: Text('Second'),
                ),
                NavigationRailDestination(
                  icon: Icon(Icons.star_border),
                  selectedIcon: Icon(Icons.star),
                  label: Text('Third'),
                ),
              ],
            ),
          )

```

2. Wrapping **NavigationRail** with **Semantics** and setting `excludeSemantics` as `true` or just wrapping it within **ExcludeSemantics** widget

*PS: I don't want to override the entire **ThemeData** from **MaterialApp** root although I don't see anything in **NavigationRailThemeData** class that references this property*

*PPS: There is a class derived from **ColorScheme** class in **NavigationRail.dart** file (towards the end) that takes in a **Semantics** widget which has all of the properties that need to be disabled, namely the **InkResponse** widget that defines the color, shape and radius of the splash/ripple*
[NavigationRail.dart](https://i.stack.imgur.com/Z7RnU.jpg)

Here is the sample code that flutter.dev provides for copy/paste convenience (works very well in dartpad.dev)

```
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

/// This Widget is the main application widget.
class MyApp extends StatelessWidget {
  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: MyStatefulWidget(),
    );
  }
}

class MyStatefulWidget extends StatefulWidget {
  MyStatefulWidget({Key key}) : super(key: key);

  @override
  _MyStatefulWidgetState createState() => _MyStatefulWidgetState();
}

class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  int _selectedIndex = 0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Row(
        children: <Widget>[
          Theme(
            data : ThemeData(
              splashColor: Colors.transparent,
              highlightColor: Colors.transparent
            ),
            child: NavigationRail(
              selectedIndex: _selectedIndex,
              onDestinationSelected: (int index) {
                setState(() {
                  _selectedIndex = index;
                });
              },
              labelType: NavigationRailLabelType.selected,
              destinations: [
                NavigationRailDestination(
                  icon: Icon(Icons.favorite_border),
                  selectedIcon: Icon(Icons.favorite),
                  label: Text('First'),
                ),
                NavigationRailDestination(
                  icon: Icon(Icons.bookmark_border),
                  selectedIcon: Icon(Icons.book),
                  label: Text('Second'),
                ),
                NavigationRailDestination(
                  icon: Icon(Icons.star_border),
                  selectedIcon: Icon(Icons.star),
                  label: Text('Third'),
                ),
              ],
            ),
          ),
          VerticalDivider(thickness: 1, width: 1),
          // This is the main content.
          Expanded(
            child: Center(
              child: Text('selectedIndex: $_selectedIndex'),
            ),
          )
        ],
      ),
    );
  }
}

```