What a weird rule! I have never ever heard about this before ! I've never liked Halloween before, and now even less
btw: Halloween was pretty unknown here up to about 5 years ago; people learned all about Halloween from certain movies, and now it is become popular too; but mostly only among adults; the habit of kids going from door to door for "trick-or-tricking" is still not done here(which was the only fun part in Halloween )

Poor black cats!!!