ngClass

HTML

<div ng-app="app" ng-controller="ctrl" class="panel-group" id="accordion">

    <ul class="nav nav-pills" ng-init="catVal = 1">
       <li ng-repeat="item in products">
           <a href=""  ng-class="{'css-class-yellow' : item.price > 50,'css-class-red' : item.price <50, 'css-class-green' : item.price > 50+50*60/100}">{{item.name}}</a>
        </li>
                       
     </ul>        
</div>

CSS

.css-class-yellow {
  color: yellow
}

.css-class-red {
  color: red
}

.css-class-green {
  color: green
}

JavaScript

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

app.controller("ctrl" , function($scope){
  
  $scope.products = [{
    'name': 'Xbox',
    'clearance': true,
    'price': 30.99,
  }, {
    'name': 'Xbox 360',
    'clearance': false,
    'salesStatus': 'old',
    'price': 99.99,
  }, {
    'name': 'Xbox One',
    'salesStatus': 'new',
    'price': 50,
  }, {
    'name': 'PS2',
    'clearance': true,
    'price': 79.99,
  }, {
    'name': 'PS3',
    'salesStatus': 'old',
    'price': 99.99,
  }, {
    'name': 'PS4',
    'salesStatus': 'new',
    'price': 20.99,
  }];
  })