functions

function prompt_colors {
  if [ -f /bin/tput ] || [ -f /usr/bin/tput ] ;
  then
    black=$(tput setaf 0)
    red=$(tput setaf 1)
    green=$(tput setaf 2)
    yellow=$(tput setaf 3)
    blue=$(tput setaf 4)
    magenta=$(tput setaf 5)
    cyan=$(tput setaf 6)
    white=$(tput setaf 7)
    reset=$(tput sgr0)

    cksum_color_no=$(echo $HOSTNAME | cksum  | awk '{print $1%7}')
    color_index=($green $yellow $blue $magenta $cyan $white)
    host_color=${color_index[$cksum_color_no]}
  fi
}

fun randomizer
cksum_color_no="$(cksum <<< "$HOSTNAME" | awk '{print $1%7}')"

I'd go for something like

black=$(tput setaf 0)
red=$(tput setaf 1)
green=$(tput setaf 2)
yellow=$(tput setaf 3)
blue=$(tput setaf 4)
magenta=$(tput setaf 5)
cyan=$(tput setaf 6)
white=$(tput setaf 7)
reset=$(tput sgr0)

color_index=($green $yellow $blue $magenta $cyan $white)
clr_no=$(( RANDOM % ${#color_index[@]} ))

echo ${color_index[$clr_no]} done $reset

I rather it not be random I can tell quickly by the host color what host I am on.