To avoid cryptic looking escape sequences, one could have the colour codes named in their .?shrc file [1]:

  txtblk='\e[0;30m' # Black - Regular
  txtred='\e[0;31m' # Red
  txtgrn='\e[0;32m' # Green
  txtylw='\e[0;33m' # Yellow
  txtblu='\e[0;34m' # Blue
  txtpur='\e[0;35m' # Purple
  txtcyn='\e[0;36m' # Cyan
  txtwht='\e[0;37m' # White
  bldblk='\e[1;30m' # Black - Bold
  bldred='\e[1;31m' # Red
  bldgrn='\e[1;32m' # Green
  bldylw='\e[1;33m' # Yellow
  bldblu='\e[1;34m' # Blue
  bldpur='\e[1;35m' # Purple
  bldcyn='\e[1;36m' # Cyan
  bldwht='\e[1;37m' # White
  unkblk='\e[4;30m' # Black - Underline
  undred='\e[4;31m' # Red
  undgrn='\e[4;32m' # Green
  undylw='\e[4;33m' # Yellow
  undblu='\e[4;34m' # Blue
  undpur='\e[4;35m' # Purple
  undcyn='\e[4;36m' # Cyan
  undwht='\e[4;37m' # White
  bakblk='\e[40m'   # Black - Background
  bakred='\e[41m'   # Red
  badgrn='\e[42m'   # Green
  bakylw='\e[43m'   # Yellow
  bakblu='\e[44m'   # Blue
  bakpur='\e[45m'   # Purple
  bakcyn='\e[46m'   # Cyan
  bakwht='\e[47m'   # White
  txtrst='\e[0m'    # Text Reset

[1] https://wiki.archlinux.org/index.php/Color_Bash_Prompt

I have a similar section in my .bashrc via a somewhat hackish loop (or two):

  ESC=$'\x1b'

  # Terminal color escapes
  colornames=(BLACK RED GREEN YELLOW BLUE MAGENTA CYAN)
  for i in ${!colornames[@]}; do
  	eval "${colornames[$i]}=\"${ESC}[3${i}m\""
  	eval "BG${colornames[$i]}=\"${ESC}[4${i}m\""
  done

  # There are holes in this sequence, so it doesn't loop nicely
  BOLD="${ESC}[1m"
  DARK="${ESC}[2m"
  UNDERLINE="${ESC}[4m"
  BLINK="${ESC}[5m"
  INVERSE="${ESC}[7m"
  RST="${ESC}[m"

  styles=(BOLD DARK UNDERLINE BLINK INVERSE RST)

  # and the PS1-safe versions of the above
  for i in ${colornames[@]} ${colornames[@]/#/BG} ${styles[@]}; do
  	eval "PS$i=\"\\[\$$i\\]\""
  done

Having color escapes in shell variables comes in handy from time to time (like faking 'colordiff' with sed).

I do that in bash for root/non-root users (root is red, non-root is blue):

    if [[ ${EUID} == 0 ]] ; then
        PS1='\[\033[01m\][ \[\033[01;31m\]\u@\h \[\033[00m\]\[\033[01m\]] \[\033[01;32m\]\w\[\033[00m\]\n\[\033[01;31m\]\$\[\033[00m\]> '
    else
        PS1='\[\033[01m\][ \[\033[01;34m\]\u@\h \[\033[00m\]\[\033[01m\]] \[\033[01;32m\]\w\[\033[00m\]\n\[\033[01;34m\]\$\[\033[00m\]> '
    fi

Interesting to think about using it across servers, though.

I used to have a different prompt color when SSH_CONNECTION was in my environment, to distinguish local terminals from remote connections. And also root/non-root, although I didn't know about $EUID and used the less-effective $(id -u).

Konsole does this automatically, at least on openSuSE linux.

It's actually just the default bash config on openSUSE, nothing to do with Konsole. It works on text-mode VTs, via ssh, etc.

I do exactly this as well as add a little blurb in motd saysing that this machine is production, tread carefully. This seems to solve a great deal of mistaken identity problems.

Is there any way to set this on directory level? I do my development in my /home/XYZ folder, and production is in /usr/local/www/XYZ and it would be great if I could set the background to red in the production dir (if I happen to wander into it somehow (which I really almost never do)).

You could put a shell script around cd that checks the current working directory every time you cd and alerts you appropriately.

A little clunky, I'll admit. I'd like to hear any more graceful solutions.

From man bash, the variable PROMPT_COMMAND:

  If set, the value is executed as a command prior to issuing each primary prompt.

e.g.:

  PROMPT_COMMAND='[[ "$PWD" =~ ^/sensitive/area ]] && PS1="be careful: " || PS1="normalprompt: "'

Pro tip: In Terminal.app you need the checkbox "Display ANSI colors" checked.

I prefer:

PS1="\[\e[1;31m\]$PS1\[\e[0m\]"