To have an animation (or any code for that matter) run after a fadeIn
you can use the callback parameter:
$('#box').fadeIn('slow', function () {
// code goes here
});
Unfortunately however, you are trying to animate colours and this is unsupported in basic jQuery. So to answer your question (how to queue an animation to run after a fadeIn), use the callback. But to answer your implied question (how to animate colours) you'll need to get the "Color" plugin for jQuery or use jQuery UI which does have support for animating colours.
More information on the animate()
method here: https://api.jquery.com/animate/