playkia It's possible, I don't have a lot fo time but the gist is, everything does not need to be themed, you know this.
So the trick is figuring out the hierarchy of the component, in this case it's a navigator with a TabBar IN it that holds the Tab you want to style.
That is 3 levels, so you really need to be able to set the skins of the Tab -> Button.
tabNavigator.tabBarFactory = function():TabBar
var tabs:TabBar = new TabBar();
tabs.distributeTabSizes = true;
tabs.tabFactory = function():ToggleButton
var tab:ToggleButton = new ToggleButton();
tab.defaultSkin = new Image( upTexture );
tab.defaultSelectedSkin = new Image( selectedTexture );
tab.downSkin = new Image( downTexture );
Edit - This may not be what you want either. You can style/texture a tab through the
dataProvider as well. That is how you can get a different
defaultSkin for each tab using the
dataProvider's data for each Tab as it's rendering.
The above code allows you to setup the tabs for a navigator. The
dataProvider skins will allow you to skin each