How to make the background of a single blogger post a different color

Why would one need this, you may well ask. Well, say you want to add a text gadget that looks like the dark background one that I have one the sidebar right here on this blog. Second one from the top. Here's the code for that:

<div style="background-color: #222222; font-family: Montserrat; font-size: 24px; font-weight: 200; line-height: 1em; padding: 10px; text-align: left; text-transform: uppercase;"><a href="https://bloggerthemetweaking.blogspot.com" target="_blank"><span style="color: #dddddd;">Blogger Theme Tweaking _ See the full collection</span></a></div>

So, all you need to do is to copy paste this, replace my text and URL with yours, then change the hex codes, the font, the font weight, the size, etc etc and hey presto - there it will be! And then, if you want this as a text widget content, just copy paste the whole shebang into that - and off you go!