更改 FLUTTER 中 TextFormField 的默认边框 colored颜色

当TextFormField处于非活动状态时，无法更改默认边框 colored颜色 .当TextFormField处于非活动状态时，将显示深灰边框 colored颜色 .那么，如何改变这一点呢？

个

Theme(
              data: new ThemeData(
                primaryColor: Colors.red,
                primaryColorDark: Colors.black,
              ),
              child: TextFormField(
                decoration: new InputDecoration(
                  labelText: "Enter Email",
                  fillColor: Colors.white,
                  border: new OutlineInputBorder(
                    borderRadius: new BorderRadius.circular(25.0),
                    borderSide: new BorderSide(),
                  ),
                  //fillColor: Colors.green
                ),
                validator: (val) {
                  if (val.length == 0) {
                    return "Email cannot be empty";
                  } else {
                    return null;
                  }
                },
                keyboardType: TextInputType.emailAddress,
                style: new TextStyle(
                  fontFamily: "Poppins",
                ),
              ),
            ),