Change border color of required Chosen jQuery select boxes - jquery-chosen

Question

Simply put, how can you change the border color of a Chosen jQuery select box? I am assuming you can do it with CSS but I can't quite figure out how.
$(".pnChosen").chosen({
search_contains: true
});
<select required class="pnChosen"></select>
I can use this to change the border color of all of them, but I only want to change ones that I mark as required.
.chosen-container{
border: 1px solid red;
}
And I also want to change the background color when they are disabled if that is possible.

Answer 1

You can use chosen's option inherit_select_classes.
Give required class on select element, and set css for this selector .required>chosen-single
$(".pnChosen").chosen({
search_contains: true,
inherit_select_classes: true
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/chosen/1.4.2/chosen.jquery.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/chosen/1.4.2/chosen.css" rel="stylesheet" />
<style>
.required>.chosen-single {
border: 1px solid #EE0000;
}
</style>
<select required class="pnChosen required">
<option>Option 1</option>
<option>Option 2</option>
</select>

Answer 2

Another option is to use the adjacent sibling combinator (+) selector in CSS to achieve the desired styling.
For example:
HTML
<select id="myselect" required="required">
...
</select>
<div id="myselect_chosen" class="chosen-container chosen-container-single">
<a class="chosen-single">
...
</a>
</div>
CSS
select:required + div.chosen-container a { ... }
This would apply the desired style(s) to your div.chosen-container a DOM element immediately following select:required. Just be aware that you may still have to establish CSS priority if you're attempting to override an existing Chosen style so your definitions can supersede any existing chosen styles.
Reference: Adjacent Sibling Combinator