css ставим стили для последних букв

$("p").lettering();

p span:nth-last-child(1), 
p span:nth-last-child(2), 
p span:nth-last-child(3), 
p span:nth-last-child(4){ 
  color:red; 
}

<script src="https://code.jquery.com/jquery-2.2.4.js"></script> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/lettering.js/0.7.0/jquery.lettering.min.js"></script> 
   
 <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Sint, dolorem quas? Beatae officiis repellendus quam dignissimos tempora laborum voluptatibus. Iste</p> 
  
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Sint, dolorem quas?</p>