Untitled

<!DOCTYPE html>
<html ng-app="app">

  <head>
    <link data-require="bootstrap@3.3.7" data-semver="3.3.7" rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" />
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>
    <script data-require="bootstrap@3.3.7" data-semver="3.3.7" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
    <script data-require="angular.js@1.6.0" data-semver="1.6.0" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.0/angular.js"></script>
    
    <link class="style-a" rel="stylesheet" href="style-a.css" />
    <link class="style-b" rel="stylesheet" href="style-b.css" />
    <link class="style-c" rel="stylesheet" href="style-c.css" />
    <script src="script.js"></script>
  </head>

  <body ng-controller="mainController">
    <button class="btn btn-default" ng-click="switch('style-a')">style-a.cssを適用</button>
    <button class="btn btn-default" ng-click="switch('style-b')">style-b.cssを適用</button>
    <button class="btn btn-default" ng-click="switch('style-c')">style-c.cssを適用</button>
    <div class="box" style="width:100px; height:100px; margin: 20px;"></div>
  </body>

</html>

// Code goes here

angular.module('app', [])
  // 使用するスタイルシートの切り替えを行うサービス 
  .factory('cssSwitch', function() {
    return {
      enableCss: function enableCss(className) {
      // 有効とするCSSのdisabled属性をはずす
      $('link.' + className).removeAttr('disabled');
    },
      disableCss: function disableCss(className) {
      // 無効とするCSSにdisabled属性をつける
      $('link.' + className).attr('disabled', 'disabled');
    }
    };
  })
  .controller('mainController', function($scope, cssSwitch){
    var classes = ['style-a', 'style-b', 'style-c'];
    
    $scope.switch = function(name){
      angular.forEach(classes, function(c){
        cssSwitch.disableCss(c);
      });
      
      cssSwitch.enableCss(name);
    };
  })

.box {
    border-radius: 25px;
    background: #73AD21;
    padding: 20px; 
}

.box {
  background-color: blue;
      border-radius: 55px;
}

.box {
  background-color: red;
}