Instead of BlurHash that needs aditionnal JS for 83 bits string, some CSS snippets can do the work for Low Quality Image Placeholders (LQIP).

The big disadvantage of pure CSS approaches is that you typically litter your markup with lengthy inline styles or obnoxious data URLs.

A blurHash like method in CSS can also be used and that's what the author is describing.
A more simpler solution is to use one color as placeholder.