Tore is on drugs, forking both perl and sed for each prompt. Of course, the following isn't perfect. Martin Krafft will be making it more efficient presently.

precmd () {
  eval toresbe="${(j:%%\{\\e\[1\;$(( (RANDOM % 7) + 31))m%%\}:)${(s::)$(print -P 'X%n@%m:%~')}}%%#"
  PS1="$(print -P ${toresbe#?} %%{\\e\[0m%%})"
}

Excuse the Amayaness of this post, especially when there are mujeres.