Thanks to a prod from @scott, I finally fixed the issue with full-screen videos looking inverted on my personal site in dark mode.
Also, just updated my blog post on how to implement quick and dirty dark mode support in a few lines of code using CSS filters with the additional code:
https://ar.al/2021/08/24/implementing-dark-mode-in-a-handful-of-lines-of-css-with-css-filters/