jQuery - Change color on click

Create a CSS class:

.clicked {
  background-color: yellow;
}

and then simply toggle that class it via jQuery:

$('.star').click(function(){
  $(this).toggleClass('clicked');
});

You could set a flag in your click function, Then add an if statement

if hasBeenClicked = true;
//...background color remove
else
//....background color changed to yellow

hasBeenClicked = true;