Dark Mode: Background and foreground colors in 'pre' tags are sometimes unreadable

#1

Hi there!

First of all, I want to thank the amazing job on the dark mode! I love it!

I do have a couple of issues with it, specifically around pre tags. I’ve been noticing that on some RSS feeds (such as useyourloaf or Swift by Sundell, the pre tags seem to have a light background for the font color, so they appear as if they’re highlighted.

An example of this is attached:

This is a little distracting to read on the web, particularly if it’s a long code block.

Some pre tags used in other sites though, are unreadable as the foreground text color is a dark blue color, which clashes too much with the background I see this in RSS feeds for MyPy Blog.

An example of this is attached: