Source: http://unix.stackexchange.com/questions/46562/how-do-you-colorize-only-some-keywords-for-a-bash-script

a.sh

{ echo line 1: PASS; echo line 2: FAIL; } | 
    awk -v "red=$(tput setaf 1)" -v "green=$(tput setaf 2)" \
        -v "reset=$(tput sgr0)" '
    { for (i = 1; i <= NF; i++) {
           if ($i == "FAIL") printf "%s", red "FAIL" reset;
           else if ($i == "PASS") printf "%s", green "PASS" reset;
           else printf "%s", $i

           if (i == NF) printf "%s", ORS
           else printf "%s", OFS 
      }}'