JSFiddle - React, Tailwind, and code Playground
HTML
<p style="font-size: 18px;">sadasdasdsasdasda<span style="background-color: rgb(0, 255, 0);" data-mce-style="background-color: #00ff00;">sdasdasda</span><span style="background-color: rgb(255, 0, 0);" data-mce-style="background-color: #ff0000;"><span style="background-color: rgb(0, 255, 0);">sdasd</span>asdasdasdas</span>dasdasd</p>
CSS
.readOnly{
background-color: #F6F6F6;
}
JavaScript
$("*").each(function(){
$(this).css('background-color','transparent');
});