In the majority of her photoshoots, her fingernails and toenails are painted in an almost white or very light skintone colour. But they are nearly always painted. This is usually used to give a more natural look in shoots, and is most likely chosen jointly by herself, the photographer and make up artist. If you look at photos of her out and about then she does use a number of different colours. Incidentally, I have seen many pictures of her wearing open toed shoes.
If you like someone to have "natural" looking feet, as you say, then why is it a concern that you were thinking she did not paint her toenails? Surely if you like them natural, you would prefer there to be no nail varnish, as that would not be "natural" looking :dunno: