Are you asking for children's literature, or YA? There are quite a few YA, morally grey, literature available; not incredibly popular, but existing. I would argue that it's difficult to really develop grey morality in a 'child''s worldview, since what a child is is more difficult to define. That said, I would say The Demon's Lexicon, by Sarah Rees Brennan, is quite morally in the grey area; the protagonists are really not very 'good', nor are they very 'evil' as in the case of an anti-hero.
...I believe that it would also be wise to introduce grey morality age-appropriately - because if someone is young enough, they might go off humanizing the villains, and humanizing a villain that would predate on someone that young would not be wise.
Are you asking for children's literature, or YA? There are quite a few YA, morally grey, literature available; not incredibly popular, but existing. I would argue that it's difficult to really develop grey morality in a 'child''s worldview, since what a child is is more difficult to define. That said, I would say The Demon's Lexicon, by Sarah Rees Brennan, is quite morally in the grey area; the protagonists are really not very 'good', nor are they very 'evil' as in the case of an anti-hero.
...I believe that it would also be wise to introduce grey morality age-appropriately - because if someone is young enough, they might go off humanizing the villains, and humanizing a villain that would predate on someone that young would not be wise.