Edit in JSFiddle

var myApp = angular.module('myApp',[]);

function Controller($scope) {
  $scope.master = {};
 
  $scope.update = function(user) {
    $scope.master = angular.copy(user);
  };
 
  $scope.reset = function() {
    $scope.user = angular.copy($scope.master);
  };
 
  $scope.reset();
}

    <div ng-controller="Controller">
      <form novalidate class="css-form">
        Name{{1+2}}:
          <input type="text" ng-model="user.name" required /><br />
        E-mail: <input type="email" ng-model="user.email" required /><br />
        Gender: <input type="radio" ng-model="user.gender" value="male" />male
        <input type="radio" ng-model="user.gender" value="female" />female<br />
        <button ng-click="reset()">RESET</button>
        <button ng-click="update(user)">SAVE</button>
      </form>
    </div>

.css-form input.ng-invalid.ng-dirty {
        background-color: #FA787E;
      }
    
      .css-form input.ng-valid.ng-dirty {
        background-color: #78FA89;
      }