Animate Effect addClass/removeClass with jQuery UI - jquery-ui

Question

In order to add a fade transition to addClass/removeClass I am using jQuery UI:
$(document).ready(function(){
$('header nav a').hover(
function(){
$('header').stop().removeAttr("style").addClass('header-pink', 'slow')
},
function(){
$('header').stop().removeClass('header-pink', 'slow')
}
)
});
My goal is: to change (with a fade animation/effect) the background-color of the parent element (header) when :hover the child element (hover nav a). The css class is very simple:
.header-pink { background: pink; }
The HTML:
<header>
<nav>
<ul>
<li>Link 1</li>
<li>Link 2</li>
<li>Link 3</li>
</ul>
</nav>
</header>
Of course, I am calling jQuery and jQuery UI with no errors:
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.8.16/jquery-ui.min.js"</script>
<script src="js/libs/jquery.effects.core.min.js"></script>
The jQuery script does not work properly because:
The class is added (onmouseover) but with no transition (fade) effect.
The class is added in a undesired way: <header style="background:
pink;"> I use .removeAtrr("style") to avoid this odd behavior.
The class is not removed (onmouseout).
Using .animate() to animate colors with jQuery UI is something I prefer to avoid because I am using variables with LESS and, of course, I want the style only to be modified by the stylesheet.
Please, check my project to get an idea. As you can see, my intention is to replace the background color of the fixed <header> with the color of the links when you place the cursor over the links. In other words, the background color of the <header> turns with a transitional fade animation/effect as blue or pink as soon as the pointer is :hover the link "Posts." or "Links." but it recovers its original state (with no css class, .removeClass()) as soon as the pointer is out with the same transitional fade animation/effect. Please note that my project is still in development and I am currently testing the effect with same properties for all the links; when I accomplish the desired result I will apply the individual properties (background-color) for every link.