Highlightjs (https://highlightjs.org/) provides simple, transparent (no ```javascript or such needed) and automatic language detection. If you don't even want to change your theme, do the following:

In settings > code injection use something like this in the header:

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.5.0/styles/monokai-sublime.min.css">

in the footer:

<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.12.0/highlight.min.js"></script>

Have a look at the styles here for example (scroll down to the css files)