In Flutter, How can I change TextFormField validation error line style?

Question

I want to set a different color for the error line created by the validator in TextFormField but I don't know how...

Answer 1

Change the color and the width to your likings providing errorBorder and focusedErrorBorder inside InputDecoration as decoration for TextFormField:

TextFormField(
        decoration: InputDecoration(
          focusedErrorBorder:UnderlineInputBorder(
            borderSide: const BorderSide(color: Colors.blue, width: 2.0))
          errorBorder: UnderlineInputBorder(
            borderSide: const BorderSide(color: Colors.blue, width: 2.0),
          ),
        ),
      ),