no.js with jquery

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<div class="firstDiv">
  Hover me
</div>

<div class="target">
  my color would change
</div>
<br>

CSS

.red-color {
  color: green;
}

JavaScript

$('.firstDiv').mouseover(function(){
	$('.target').addClass('red-color')
})