Load CSS Theme Dynamically on user selection in AngularJS

To implement themes in application I create multiple css files with different styles like (red, green,blue).

Red.css

body
{
font-family: "Source Sans Pro",Calibri,Candara,Arial,sans-serif;
font-size: 15px;
line-height: 1.42857143;
color: #333333;
background-color: red;
}

Blue.css

body
{
font-family: "Source Sans Pro",Calibri,Candara,Arial,sans-serif;
font-size: 15px;
line-height: 1.42857143;
color: wheat;
background-color: blue;
}

Green.css

body
{
font-family: "Source Sans Pro",Calibri,Candara,Arial,sans-serif;
font-size: 15px;
line-height: 1.42857143;
color: chartreuse;
background-color: green;
}

Then I create an app.js file for AngularJS, in which I declare my Angular module and controller.

angular.module('ThemeApp', [])
.controller('mainController', function ($scope) {
// set the default theme
$scope.css = 'Red';
// create the list of themes
$scope.bootstraps = [
{ name: 'Red', url: 'Red' },
{ name: 'Blue', url: 'Blue' },
{ name: 'Green', url: 'Green' }
];
});

In the above code I declare a module "ThemeApp" and then attach a controller with this module. In the controller I declare an object array with all available theme that implements my application. I set one of theme by default for application for the first time.