I too strongly prefer the prefix : for uniformity with other Lisp
dialects. At least CL, Emacs Lisp, Clojure, and Hy all have it. Lisp is
also a prefix language, so a prefix syntax is consistent with the rest.

I'm not aware of any language that uses -> or . or something like that
for keywords. Smalltalk uses postfix : but it's an infix language.