Change TextField’s Underline in Flutter

You can also change its color by following ways.

1. Wrap your TextField in Theme and provide accentColor

   Theme(
     data: Theme.of(context).copyWith(accentColor: Colors.red),
     child: TextField(),
   )
   

2. Using inputDecoration property.

   TextField(
     decoration: InputDecoration(
       focusedBorder: UnderlineInputBorder(
         borderSide: BorderSide(color: Colors.red),
       ),
     ),
   )