I am looking for a javascript library that can be run in different servers, but not node.js (for a WordPress site), capable of doing this: https://color-wander.surge.sh/ or something similar.
How about something starting with a client side option you can upload to any web server afterwards ?
The are quite a few creative coding javascript libraries out there. The simplest to get started with I can think of is p5.js
Have a look at the p5.js Brownian Motion example
On Wordpress, have a look at this article:Embedding p5.js in a WordPress entry
Additionally there's an p5.js video course