How to use a hex color in Material App theme?

You may have this:

theme: ThemeData(
        primarySwatch: Colors.green,
      ),

And you may want to use a hex color. You can do it like that:

theme: Theme.of(context).copyWith(
        colorScheme: Theme.of(context).colorScheme.copyWith(
              primary: const Color(0xFFC0CDB5),
            ),
      ),