well technically speaking grey is not a color but a shade.. Anyway tell us if you are on windows because it vary a lot between old and earlier versions. If on old windows look at ansicon which enables proper ansi escape on neanderthalian cmd.exe

Here you have all available ansi colors by category: Grey0 is in the 256Colors category and does not work in older cmd.exe.

If you import :constants256 then you can try using the constant GREY0

The following works for me

perl -e "use Term::ANSIColor qw(colored); print colored(['grey0'],'gre
+y0 text on default background',$/);"
[download]

L*