You can check the text of each element and set its CSS color property if it matches the regular expression.

var regex = /(apples|oranges)/g;

$('body a, body p, body div').each(function() {
    var $this = $(this);
    var text = $this.text();
    if (text.match(regex)) {
        $this.css("color", "grey");
        if($this.children().length===0){
          $this.html(
              $this.html().replace(regex, '<span style="background: #fa7373;">$1</span>')
          );
        }
    }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div>
<p>I bought some apples.</p>
<p>Apples are £2 per kg.</p>
</div>

<hr>

<div>
<p><a href="oranges.html">I bought some oranges.</a></p>
<p>Oranges are £1.50 per kg.</p>
</div>

<hr>

<div>
<p><a href="pears.html">I bought some pears.</a></p>
<p>Pears are £1.80 per kg.</p>
</div>

I’m searching a web page containing a list of products for keywords from an array. When it finds any word in the array it highlights it with a red background. That works fine. Now, when it finds the keywords I want it to make all of the text for that product (within the <div> tag) to have a light grey colour so I can easily ignore that particular product when scanning down the page. How can I do this? Here’s the demo: JSFiddle

Here’s the HTML:

<div>
<p>I bought some apples.</p>
<p>Apples are £2 per kg.</p>
</div>

<hr>

<div>
<p><a href="oranges.html">I bought some oranges.</a></p>
<p>Oranges are £1.50 per kg.</p>
</div>

<hr>

<div>
<p><a href="pears.html">I bought some pears.</a></p>
<p>Pears are £1.80 per kg.</p>
</div>

Here’s the JavaScript:

var regex = /(apples|oranges)/g;

$('body a, body p').each(function() {
    var $this = $(this);
    var text = $this.text();
    if (text.match(regex) && $this.children().length===0) {
        $this.html(
            $this.html().replace(regex, '<span style="background: #fa7373;">$1</span>')
        );
    }
});