Flutter textfield background color on focus

It looks like it's caused by the splash effect on the textfield. I couldn't find a way to disable it for that specific widget but you can make it transparent by wrapping your TextField in a Theme widget and setting the splashColor to transparent:

Theme(
  data: Theme.of(context).copyWith(splashColor: Colors.transparent),
  child: TextField(
    autofocus: false,
    style: TextStyle(fontSize: 22.0, color: Color(0xFFbdc6cf)),
    decoration: InputDecoration(
      filled: true,
      fillColor: Colors.white,
      hintText: 'Username',
      contentPadding:
          const EdgeInsets.only(left: 14.0, bottom: 8.0, top: 8.0),
      focusedBorder: OutlineInputBorder(
        borderSide: BorderSide(color: Colors.white),
        borderRadius: BorderRadius.circular(25.7),
      ),
      enabledBorder: UnderlineInputBorder(
        borderSide: BorderSide(color: Colors.white),
        borderRadius: BorderRadius.circular(25.7),
      ),
    ),
  ),
);

“Flutter Textfield background color”

*Change border color of TextField in flutter

TextFormField(
        decoration: InputDecoration(
          labelText: "Resevior Name",
          fillColor: Colors.white,
          focusedBorder:OutlineInputBorder(
            borderSide: const BorderSide(color: Colors.white, width: 2.0),
            borderRadius: BorderRadius.circular(25.0),
          ),
        ),
      )

text fieldform color flutter

TextField(
  style: TextStyle(color: Colors.red),
  decoration: InputDecoration(fillColor: Colors.orange, filled: true),
)

Flutter TextFormField background color

TextFormField(
    decoration: InputDecoration(
        labelText: "Resevior Name",
        fillColor: Colors.white,
        filled: true, // dont forget this line
        ...
    )
    ...
)

Flutter textfield label color

labelStyle: TextStyle(
    color: Colors.white,
)

Color textfield text flutter

TextField(
  style: TextStyle(color: Colors.white),
  ...
)