Current Perl documentation can be found at perldoc.perl.org.
Here is our local, out-dated (pre-5.6) version:
In general, you don't, because you don't know whether the recipient has a color-aware display device. If you know that they have an ANSI terminal that understands color, you can use the Term::ANSIColor module from CPAN:
use Term::ANSIColor; print color("red"), "Stop!\n", color("reset"); print color("green"), "Go!\n", color("reset");
Or like this:
use Term::ANSIColor qw(:constants); print RED, "Stop!\n", RESET; print GREEN, "Go!\n", RESET;