Oh the irony. White on purple article, and it's not even white.
Fortunately, they changed it to some sane color.
https://userstyles.org/style_screenshots/199552_after.png?r=...
I used to make user style just to make it readable. The top right is the original color of GitHub dark theme, and left bottom is the one I modified.
Someone set the color must forget how srgb works. #808080 is not half of the light level. It's about 1/3.