How to make path prompt easier to read by color-coding each `/` (forward slash)?
If I understand the question correctly, you want to have your prompt display the entire path of your current directory in blue but with each of the forward slashes ("/") in pink.

Unfortunately, you can't do this in your prompt.  



Use the builtin precmd () function.

ZSH gives us a precmd function which is similar to Bash's PROMPT_COMMAND.  These allow a command to be issued before the prompt is displayed.

I also wouldn't recommend a long prompt anyway as it makes usability very difficult when entering commands. Putting the full directory above your prompt is much better from a UI standpoint.  The following code accomplishes that. 

Simply put the following in your ~/.zprofile.

precmd ()  { printf "\n"; pwd | awk -F "/" ' {for (i=1; i&lt;=NF; i++) printf "\033[01;34m"$i"\033[38;5;206m/"; printf"\n" }' }


And here are the results:



The above screenshot is my iTerm window showing that I have traversed deep into my /Applications/Firefox.app directory with the current directory formatted in blue separated by pink forward slashes.



How it Works...

I've expanded the one line premcmd function above so that it's multi-line and added in some variables so we can better see what's going on.

precmd() {
printf "\n";
pwd | awk -F "/" '{ blue="\033[01;34m"; \
                    pink="\033[38;5;206m"; \
                    for (i=1; i&lt;=NF; i++) \
                      printf blue $i pink "/"; \
                      printf "\n"
                   }'
} 


Here's what it all means:


printf "\n" prints out a new line char.  This is for aesthetics.
pwd returns the working directory name (man pwd) which is then piped ("|") to the next command, awk (man awk).
-F "/" defines the field separator to the forward slash; awk's default is a space.  I kept my prompt to it's short and succinct setup.


Within the awk "program," delimited by the braces ("{" and "}") we have the following:


variables blue and pink are set to their ANSI escape codes \033[01;34m and \033[38;5;206m respectively.   
We then have a for/do loop that iterates through each of the fields that awk has processed.  NF is the total number of fields.
printf blue $i and printf pink "/" prints out the directory name in blue and the forward slash in pink