Using ng-repeat with random

I'm trying to randomly generate a list, in which every item is clickable.

  <ul class="list-group">
    <li class="list-group-item" ng-repeat="user in users | orderBy: random" ng-class="user.value && user.color" ng-click="changeValue(user)"> </li>
  </ul>

So, on click I want it to change the value of the item and also the colour.

I already can randomly generate the list with the following function:

$scope.random = function() {

  return 0.5 - Math.random();

};

The problem I'm facing is that whenever I click a list item, they re-arrange randomly. I want them to display randomly at the beginning and then stay in the exact same order after I click them. How can I avoid the re-arrange?

Here's a plunker with a practical example:

DEMO

Thank you.