AngularJS Fiddle

Get Started With Angular

HTML

<div ng-controller="MainController">
  <button type="button" class="btn btn-default" ng-click="chngcolor()" ng-style="color">Change Color</button>
  <button type="button"  ng-style="color" class="btn btn-default" ng-click="chcolor()">Pre Color</button>
</div>

JavaScript

// Initialise Angular
var app = angular.module('app', []);

// Main Controller
app.controller('MainController', ['$scope', function($scope) {

  // set default color
  $scope.color = {
    'background-color': 'white'
  };

  $scope.chngcolor = function() {
    $scope.color = {
      'background-color': 'white'
    };
  };

  $scope.chcolor = function() {
    $scope.color = {
      'background-color': 'green'
    };
  };
}]);