You could use ANSI colors...

my @CHARS = (
"\033[1;30;40m ", # dark grey on black
"\033[1;30;40m@", # same thing, but prints '@' instead of ' '
"\033[1;30;47m@", # dark grey on light grey
"\033[1;30;47m ", 
"\033[1;36;47m@", # light blue on light grey
"\033[0;37;46m@", # light grey on light blue
"\033[0;37;46m ", 
"\033[0;34;46m@", # dark blue on light blue
"\033[0;36;44m@", # light blue on dark blue
"\033[0;36;44m "
);
[download]

Now, these are strings as opposed to characters, but it still works.