AngularJS ng-class.

HTML

<div ng-app="myApp" ng-controller="MainCtrl">
    <div ng-class="test">Test.</div>
</div>

CSS

.red {
    background-color: red;
}

.green {
    background-color: green;
}

.blue {
    background-color: blue;
}

JavaScript

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

app.controller('MainCtrl', function($scope) {

$scope.test = "customclass";
});