Your editor probably can do that! Emacs and VSCode at least both can. Search for 'rainbow blocks' or 'rainbow parens' or 'rainbow delimiters' extensions.
This is the standard coloring that comes with Coleslaw which is a Jekyll alternative written in common lisp: https://github.com/coleslaw-org/coleslaw. I believe the website is using that or at least it uses one of his default themes.