Easily add colours to bash scripts

RED="$(tput setaf 1)"
GREEN="$(tput setaf 2)"
YELLOW="$(tput setaf 3)"
WHITE="$(tput setaf 7)"
RESET=$WHITE

echo "${RED}An error occurred${RESET}"
echo "${YELLOW}Warning: Be careful${RESET}"
echo "${GREEN}Everything is groovy${RESET}"

(source)

Old, naive way:

GREEN="\[\033[32m\]"
YELLOW="\[\033[33m\]"
RESET="\[\033[0m\]"

Determine a day's ordinal suffix: 1st, 2nd, 3rd, 4th, etc.

e.g. for dates you don't want to display "19 July" but rather "19th July":

my $ordinal;
if ($foo =~ /(?<!1)1$/) {
    $ordinal = 'st';
} elsif ($foo =~ /(?<!1)2$/) {
    $ordinal = 'nd';
} elsif ($foo =~ /(?<!1)3$/) {
    $ordinal = 'rd';
} else {
    $ordinal = 'th';
}

Bonus points if you can integrate this with DateTime's strftime() method neatly.

(source)

Colouring terminal output

• Emacs, in a term buffer: configure font-lock-keywords for term-mode
• spc (Supercat)
• grc (Generic Colouriser)
• highlight
• histring
• pygmentize
• grep --color

Thanks to StackOverflow

UPDATE: You can actually do this yourself with pretty much any programming language that has an ANSI colours library.